Welcome!
Here you may find what you need if you want to install a texturepack and its additions.
As some people may be afraid of reading or know the basics already this post is separated into two sections - the Quickstart and the Full Guide (thanks Timmie for hinting me towards there).
If you are absolutely clueless the Full Guide may be your choice. Else just go on with the Quickstart.

Quickstart

• 1) Download the latest Sphax Texturepack according to your MC-version to your %appdata%/.minecraft/texturepacks directory (now refered to as TP.zip)
  
• 2) Be sure to patch your minecraft.jar to be HD-texture-compatible (MCPatcher or OptiFine)
  
• 3) Install all the mods of your choice
  
• 4) Download the additions from this forum for your add-ons to a temporary place
  
• 5) Open your original TP.zip (from 1))
  
• 6) Now open up your downloaded texturepack-addons one after another and drag&drop them into your TP.zip
  
• 7) Start up MineCraft and enjoyed the sphaxified mods.
  

Full Guide

STEP 1 - Getting the basis:

We'll start using a fresh installation of MineCraft! If you are unsure
how to get all your modified thingies out:

Browse on your harddrive to
C:/User/_USERNAME_/AppData/Roaming/.minecraft/

where _USERNAME_ is equivalent to your username on Windows (wouldn't have guessed that, right? ).
A faster way is this:

Start -> Execute (or [Windows-Key] + [R]) - and type
%appdata%/.minecraft/

Now you should see something like this:

Delete all the content and start your Minecraft.exe once again. It will now force to create
the files anew.

Congratulations. You finished the step to get a clean MineCraft-installation!

STEP 2 - Getting on with basis:

Now you seem like you wanna have those kinky nice textures by Sphax?
Go right on and download the texture-pack from this site! (bdcraft.net if you already forgot)
I recommend the [128x]-pack as most additions use that size as well - PLUS the load of your game is lower than with higher resolution textures.
If you are too lazy: /download-purebdcraft-texturepack-for-minecraft

Put the PACKED file (don't extract!) in (see above)
%appdata%/.minecraft/texturepacks/

Now we need MineCraft to be able to handle those nasty higher resolution textures.
I'll give you two routes here - the OptiFine and the MCPatcher route. I would recommend OptiFine as most people can report that you get more FPS and a lower load!

STEP 2.1 - The recommended OptiFine Way

Now start with installing MineCraft Forge (or - see below for reasons - Risugami's ModLoader) by following the instructions on the page.
You can open up minecraft.jar with WinRAR e.g.

ATTENTION: Be sure to open up minecraft.jar not minecraft-1.2.5.jar or similar. The file with version-number is your backup!

Don't worry if there is no META-INF folder - it may not be created if you haven't started MineCraft after fresh installation once. If it's there - be sure to delete it!
The same way Risugami's ModLoader is installed!

ATTENTION: Should you not use MineCraft Forge (e.g. if you favor playing without technical packs) you may need ModLoader separately! Again, check the author's instructions then. If you need Forge anyway there is no reason to install ModLoader itself as Forge includes ModLoader anyway.

Now you want to browse to the OptiFine-Thread and choose the package that suits you best. There are many options available so read carefully.

ATTENTION: It's important to install OptiFine AFTER installation of MCForge/ModLoader!

STEP 2.2 - The MCPatcher Way

Patch it to your likings (though i recommend the options shown below).

MCPatcher will now patch your minecraft.jar located in "%appdata%/.minecraft/bin/" as well as it creates a backup of your original one (so you can UNPATCH back to original jar).
If you wonder: I installed latest Connected Textures Mod manually afterwards.

Now you could run MineCraft and enjoy the standard game with Sphax' awesome style.

I bet you are not here for that, right? Okay ... let's go on further.

Now install MineCraft Forge 3.3.8.152 (recommended version).

ATTENTION: Be sure to open up minecraft.jar not minecraft-1.2.5.jar or similar. The file with version-number is the backup by MCPatcher!

Don't worry if there is no META-INF folder - - it may not be created if you haven't started MineCraft after fresh installation once. If it's there - be sure to delete it!
The same way Risugami's ModLoader is installed!

ATTENTION: Should you not use MineCraft Forge (e.g. if you favor playing without technical packs) you may need ModLoader separately! Again, check the author's instructions then. If you need Forge anyway there is no reason to install ModLoader itself as Forge includes ModLoader anyway.

STEP 3 - Mod your MineCraft the Sphax-way:

Most of you love those little technical mods out there and don't want to miss the Sphax-textures on them.
Here you'll get the following:

- How to install mods
- How to extend your texturepack (referenced here as TP) with community-added mods

I'll do it with following mods:

• Equivalent Exchange 2 v1.4.6.6 (http://equivalentexchange.wikispaces.com/)
  
• RedPower 2 (http://www.eloraam.com)
  
• BuildCraft 3.1.5 (http://www.mod-buildcraft.com/)
  
• Industrial Craft 2 v1.97 (http://www.industrial-craft.net/)
  
• Forestry v1.4.3.8 (http://forestry.sengir.net/wiki/)
  

STEP 3.1 - Install your mods:

Now go on and download all the mods you want and install them according to the instructions the authors gave you.
Most mods just go as .zip or .jar to your "%appdata%/.minecraft/mods/" folder. If it doesn't exist just create it.

ATTENTION: Be sure to read the author's instructions. For example on forestry: It is recommended to remove the forestry-API
from Equivalent Exchange 2 to avoid clashes - though newer versions of EE2 seem to not incorporate forestry-API anymore.

Your mods-folder should look like this (as far as you used those mods talked about above).

STEP 3.2 - Sphaxify your mods

Thanks to the community (I think we must mention CadenDonut, HanFox, pcmaster160 and sorts here especially!) many of technical mods around were sphaxified.
So we browse to the forums MODS support - Patches section and look for our mods.

Or we just use pcmaster160's Overview of all Sphax Addon Project Textures.
The Sphax Addon Project emphasizes those technical mods and their additions. Be sure to check the thread out!

We find those mods:

• Equivalent Exchange 2 - CadenDonuts,Hanfox,Amon
  
• RedPower 2 -Amon,Timmie3054,CadenDonuts,PCMaster160,HanFox
  
• Buildcraft -CadenDonuts
  
• Industrial Craft 2 (128x)(64x) -Ruyan,Hanfox,PCMaster160,Caden
  
• Forestry -Hanfox,PCMaster160, Amon
  

Gladly thanks to those people our mods are all supported. We go really crazy now and download their 128x-version-.zips to a temporary folder.
Why the 128x version? Because our base TP is 128x as well. You downloaded 64x because your rig isn't powerful enough to handle your hundreds
of mods and textures? Most additions come in 64x as well! Use these instead.

Now open up your Sphax TP .zip-file (has to be in "%appdata%/.minecraft/texturepacks/", remember?) and keep it open. You'll need that window for a while now.
The thing to do now is the following.
We open up our downloaded texture addons one after another and drag&drop its contents over to the TP .zip-file.

After spending some time now dragging and dropping all those folders over to your former unmodded TP it should look like this:

See those folders the arrows are pointing at? Right! These are the folders you dragged in there - they contain the textures the mods will use after selecting the TP in MineCraft.

ATTENTION: Remember that if not said otherwise it's simple as that! It's the same for Tekkit, too. Just be sure you get the most up to date textures because the mod authors often add
or alter their sets - so have to do our texture addon gods.

STEP 4 - Start up the engines ... VRUMM!

Here you go. You have completed the little tutorial and should be proud.
Your honoration is still to come - just one more thing to do.
If you did everything right you should be able to start up MineCraft!

If you happen to land on the mainscreen you should find the following:

See how actual MineCraft tells you how many mods are loaded? MineCraft Forge is listed there as well!
Hooray! Now go and click "Texture Packs" and select your Sphax TP.
It may take while because it became huge after adding the additional files (around 41MB here).

You got it working?
Hooray!

*gives you the 'I did what Amon said - I don't have to feel unworthy to be here'-medal*

Changelog: