I have a Compaq/HP Presario SR1630NX (Circa 2005) 2.5 GB RAM, AMD Athelon 64 3500+ 2.19 GHz, Windows XP SP3, fully updated.
A few days ago I had an infection, so far unidentified, with the message "Application cannot be executed ...." I tried several things I saw here, including rkill and OTS. I was able to run rkill by starting it while the message box was up and rkill succeeded in cleansing memory, at least. The I went back to run through the Malware and Spyware Cleaning Guide, but when I rebooted after removing the temp files with TFC, I was unable to successfully run rkill again. Perhaps I was just tired.
Anyway, the next afternoon I called the Geek Squad (part of Best Buy) and the associate recommended I run my anti-virus program (AVG 9.0, as it happens) when the computer was in Safe Mode. I did so, and the next morning it had finished and left a log of its actions. Nothing seemed to stand out but I rebooted, again in Safe Mode and there were no untoward messages. I re-booted in safe Mode with Networking and still no problems. (I don't recall how much networking I was able to see.) Then I rebooted and found that all three user IDs were OK and free of pesky messages.
But in mine, while FireFox works (I'm using it now) IE and Chrome do not. I don't recall how I got them to work in the first place. I'm using a 2Wire 1701HG Gateway DSL Modem which provides DHCP, as expected by my computer.
As I said, FireFox works, as does BOINC. In another (non-priviledged) UserID, IE also works, but not in mine.
I can attach the log from AVG if desired. I can't find the one from rkill, but the dastardly program rkill killed had a directory and a name which I would call randomly generated.