Network not working on XP Home

I have a problem with a laptop with Windows XP Home SP2. My antivirus found
and deleted a trojan in the file comsvcsw.dll.bak in the SYSTEM32 folder.
All of a sudden, the networking ability is gone, including Internet access.
If I do an IPCONFIG, it says: "An internal error occurred, the request is
not supported". I have tried repairing the Local Connection, uninstalling &
reinstalling the network cards (it has wired and wireless), and running
every TCP stack and Winsock repair utility I can find, to no avail. The
situation is further complicated in that the System Restore apparently has
never worked; there are no restore points, even though the feature is turned
on. On top of that, for some unexplained reason, the laptop shuts itself
off any time it is booted with a Windows XP setup disc, including the
manufacturer-specific one it came with! I am at a loss as to what to try
next, as I can't even repair or reload XP at this point!

- Ben