Windows update can be configured to 'advise' of updates but not download:
Control Panel -> Security Center -> Automatic Update
Select 'Notify me but don't download updates'.
This will then put a yellow shield in your system tray when updates are available.
Antivirus, most packages can be configured to do the same.
Messenger programs, Yahoo, MSN Gtalk etc. I would sign out and exit those.
Often overlooked, some have Disk De-fragmentation programs that will work in the background when they think the system is idle.
Disk Keeper seems to regard low disk IO as an indicator of an idle system and will commence a defrag whilst IL2:FB is running.