Well. I did something stupid.
I use a firefox plugin that auto-scans every download once it's complete. Well, I was inpatient, and ran it while the scan was loading up. First windows update was disabled. Then my Norton Auto-Protect icon vanished. Running Norton manually produces "This is not a valid Win32 application." So I reinstalled. The uninstall wouldn't complete, so I used Symantec's product removal tool, first. Install would not complete. Installed Trend Micro. Wouldn't install. I tried Avast. "Not a valid Win 32 application. Used Microsoft's, Avasts, and someone else's downloadable virus removal tool. (Stinger, I think?) Microsoft's wouldn't complete, Avast could not scan MANY .exe files, and the other just didn't find anything.
On a side note, my icons start vanishing, or are incorrect, in the start menu, desktop, task bar, and quick menu. (Oddly, the system tray's icons are okay.)
This isn't adware; I'm certain this is a virus, from it's apparent attacks on any and every virus scanner I've tried. Is a HijackThis log appropriate for this problem? I'm planning on a new computer in the near future, so I'd like to avoid the trouble of a full re-install, if possible.