I can't say that I'm the most familiar with the HQ "mod," but I'll give you what I know. I put mod in quotation marks, because it's not a mod in the sense that it's a .package file you can drop into your Mods folder, but it's instead a modified GraphicsRules.sgr file that goes in the main game files.
Anyways, GraphicsRules.sgr is located in Program Files (x86) -> Electronic Arts
or Origin Games (depending on how you installed the base game) -> The Sims 3 -> Game -> Bin. The HQ Mod provides a file that replaces GraphicsRules.sgr, so backup your original file (this is important! If you want to take out the HQ Mod, you need the original to go back in to your game files. So move the original to your desktop or a thumb drive), and then replace it with the new file.
I can also PM you links to a couple of helpful sites for more (and better) info.
For anyone wondering what the HQ Mod is, it's a modification that allows for higher-resolution textures in the game.