This is easy thing to do, but it might crash minecraft and delete your server list, it is that sensitive, there are two types of installations • 1 click Installation • Advanced installation The 1 click installs are easy to do and never crash minecraft. Advanced installations are more tougher and require certian programs to install those mods NOTE: This is the installation for WINDOWS And for SINGLEPLAYER!!!! Step 1: download mod, it should be a zip, or a rar Step 2: put mod on desktop or if multiple mods and want to backup them make a folder and call it whatever you want Step 3: unzip mods, this can be done two ways: •WinZIP,7-ZIP, or WinRAR •Windows Explorer I perfrer WinZIP for installs of mods and both versions work Step 4: unzip contents inside including the .class files in zip file Step 5: for Windows XP click start, and click run and type %appdata%, it should lead to Application Data,find .minecraft and open bin and open minecraft with the programs to open the zip(WinZIP,7-Zip,WinRAR. Windows Explorer will not work), move .class files in and delete the meta-inf folder and done. Im sure vista and seven are similar to this, enjoy modding!!!!