Painful Dropper.gen infection

This machine running XPPRO was entombed since 2009, recently turned on after forgetting had been acting infected. I do not have the original Windows install disk, but I do have an xppro sp2 disk, which I tried to use with 'sfc /scannow'. System file check didn't recognize disk. Missing Windows search assistant, tried to reinstall srchasst.inf, missing msgr3en.dll. Ran Avast, found Dropper.gen in cobian backup's .exe file. Quarantined. Now it will only boot into safe mode, regular boot hangs at 'starting windows'

Problem with old McAfee install, cannot uninstall in safe mode. Also messages saying missing 'mytilus.dll' (related?).

Ran 'read me' instructions, files attached. Skipped CCLeaner b/c too much missing. Could not run MGtools, got processdll.exe, .net framework install failed as well.

In running a/v programs off USB stick, noticed new infection of external drive g: by a trojan in system volume information and transferred infection to a laptop by copying a non-executable file from the memory stick to the laptop's desktop. (You may be hearing from me on that issue as well, in another thred). Hitman pro and tdsskiller scans returned 'no threat'