Not entirely sure what you meant by "Endrive" (External?), but its the same as installing on any other drive. When the game installs, just pick which drive you want it on and it'll take care of the rest.
As for saving what you have, don't pull the whole folder. You can do that but it'll cause confusion later. Just pull the User Data Folder out of your install. You'll have to run Data Base Rebuild later when you throw it all back together with a new install.
I would point out, that as long as you have a decent Anti-Virus and some kind of Malware tool, you shouldn't need a windows reformat..... I admit its one of the only "Garunteed" ways to remove a virus, but unless you got hit with a newer virus, most of the newer tools are more then capable of dealing with what I'll call the "Usual evil". If your registry has been screwed 6 ways from sunday, then yea, a reformat is probably your best answer, but if this is just normal adware (Browser Hi-jacks and what not), you shouldn't need to reformat if you can get some of the better tools....
Good Luck,
Falcus
