So, have you got 3 partitions or 2?
Assuming you have 2 and C is your boot drive...
leave your OS on the primary drive, but move all your files to your new F drive. Move your My Documents folder; make a new folder for it on your F drive, and right-click on the My Documents icon from the desktop or start menu and click properties. Click the move button, and it will let you select a new location for your My Documents folder, and copy the stuff over.
Save the installation files and stuff for things like Firefox on your second drive, but still install them on C. You can't just move program folders to another drive. You can install them there, but you'd have to uninstall them and reinstall at the new location. I'd keep basic stuff like your browsers on C drive because when you reformat you'd need to reinstall that even if you installed it on F.
Keep no data on your boot drive, just OS and programs if you want. Keep program installation files and/or backups of your program CDs on your second drive if you like. I usually use 20-30gb partition for Windows XP.