Phil,
Before I start I know the problem - your a Man U supporter and it's a well documented fact that Sasser loves to infect Man U supporters PC's - Just Kidding,
All I can suggest is:
Get ready with the [shutdown -a] command (Abort Shutdown)
This cancels the countdown. You could also create a notepad file with the following copied into it:
_______________
@echo off
shutdown -a
_______________
Change "Save As Type" from "Text Documents" to "All Files" then save this notepad file as "Cancel Shutdown.bat" onto your desktop - now when it starts to countdown just double click the icon to cancel shutdown.
Now goto:
Start>Programs>Accessories>System Tools and click on System Restore. Disable this - it stores loads of historical crap such as past viruses and spyware which can still be "live" even though it is archived in a restore file.
Download the following to a folder on your C: drive -
Microsoft Patches:
KB823980
KB824146
KB835732
McAfee AVERT Stinger from:
Spybot S&D
Lavasoft AdAware
Hijack This
After you have downloaded the above software disconnect your internet connection (either disable the connection or simply unplug your cable) and run stinger.exe, this will scan your machine with an up-to-date removal tool to make sure there is no malicious software on your machine. Then run Spybot - just agree with all the options on startup - if your not happy with any changes it makes you can uninstall it at a later date also install AdAware ready for use after.
When stinger has finished running (it may take a while depending on the size of your hard drive - also it will auto delete any malicious software found).
Now run Spybot and when the scan has finished the scan then click on "fix selected problems", you may find it has at least one entry that it can't fix which will be a "DSO Exploit" this is just a Microsoft entry in the registry.
For safe measure run Lavasoft AdAware and see if it finds any other spyware.
Once you have cleared all the crap off your machine then go ahead and install the 3 patches I mentioned. Even if they are already there or you have auto updates on and you think they have downloaded still reinstall - I don't trust auto updates.
Say no to all requests for a reboot and then reboot when the last patch is installed.
Now in theory (oh what a good thing theory is !) this should have sorted your problems and you can reconnect your net connection and Bob's your Uncle and Fannys your live-in Aunt all is well again.
If not then run Hijack This - run a scan with a log and post the log on to the forum (copy n paste) and someone may be able to spot something...
Hope this helps mate,
Chris.
Man United are short sited tra la la la laaa la laa laa laaaaaa ;o)