I installed Slaye's EVOX installer 2.1, and now that 2.5 is out, I wanna upgrade my Dashboard and programs w/out losing all the games i have backed up. It will take too long to back them up again.

Dose the Slayer's 2.5 upgrade option get rid of all the stuff in my HDD, and starts it off fresh?

Or does it just upgrade Evox, XBMP, etc.?

Just FTP over the specific programs you want. Evolution X is only two files (evoxdash.xbe and evox.ini). The other programs are in their own directories. No point in using an autoinstaller to upgrade programs.