I'm stumped and desperate!

Hello!
I've recently posted my frustration, having been been plagued with a
slight problem shutting down. When I click on, "TURN OFF COMPUTER", a
dialog box pops up, that reads, and I quote: "Recent is a Windows
System folder and is required for Windows to run properly. It cannot be
deleted"

My post gave me a few responses which indicated a Trojan Horse. I
clicked on the HELP link provided and sure enough, there is my error
message, and the answer is: - a Trojan Horse.

I downloaded the latest Norton AntiVirus definitions, and did a
complete scan. NOTHING!

I downloaded the latest SPYSWEEPER defiinitions and did a complete
scan. NOTHING!. (Spysweeper claimns to find Torjans as well as
Spyware).

Can someone offer me a clue as to what my next step can possibly be?
I'm afraid of infecting my eMail correspondents, even though Nortons
also scans my outgoing eMail.

.