Windows File Sharing problems

Update:
It's working now. Had to go to local security settings and reset "Access this computer from the Network".

This is all copied/pasted from another forums that I frequent. Let me know if something isn't clear:

Ever since I built my roommate's computer (XP SP2), I would log into my "server" (just a headless XP SP2 machine) via remote desktop, and grab data from his harddrive via an administrative share. I would map this share to the Z: drive, but only to make it easier for me - I didn't feel like typing \\computername\e$ every time.

Now, nothing on my server or on my network has changed. I can still log into my server and do everything I did before, EXCEPT get on my roommate's computer. All of this happened just after he accidentally downloaded one of those AIM/MySpace viruses. He said he ran a virus scan, but last night I double checked. I updated AVG, ran it, and it found some trojan (backdoor.generic2.mdv I believe). AdAware only found some trivial stuff (cookies mostly), and HijackThis only found a reference to that trojan, which I removed.

I've also rebooted both computers, but to no avail. Additionally, I've double checked security and permissions on the drive, which appear to be fine. The things I haven't tried but plan on doing after I get home from work tonight are:

• I noticed he had windows update turned off - so run updates and see if that fixes anything
• Create an entirely new user account to make sure it's not some weird account thing.
• Double check NTFS permissions to make sure some special permission hasn't been set.
• Rerun AVG and/or TrendMicro Housecall

Here are the error messages I'll get (but not at the same time) when I try to access his computer (Yes I named his computer brucelee. Maybe chucknorris would be better):




I really don't want to reinstall XP and everything, because that will waste my Saturday.

Does anyone have any ideas or know of anything I haven't checked or thought of?

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Followup:

Alrighty, update for what I've done.

• He must be running Microsoft Update himself - there were no critical updates (just three optional ones, but they weren't important)
• Created a new admin account called test. I was unable to use that account to get on any share either, even after specifically giving that account full read/write permissions on the share.
• Owner of the E drive (which I'm trying to access) is the Administrators Group. I reapplied it, but it did nothing.
• Reran AVG with newest defs, but showed nothing.
• Tried to run housecall, but neither Firefox or IE would let me
• Figured I'd try AimFix - it found and deleted an lsass process. Didn't help me connect though.

I talked to craig about how bad he messed stuff up and told him I may need to flatten and redo, but he didn't want that at all. He's confident I'll find something.

At this point I'm leaning toward my initial suspicions that there's some registry setting or whatnot that got changed. I'm going to spend some of today googling registry entries for filesharing.

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To clarify, virus that AVG found was found at c:\windows\scvhost.exe [sic]. It appears to be some sort of IRC based trojan. Subsequent scans have revealed nothing else.

Also, I'm at work right now, and can only access my server, not his computer directly. After he leaves for work, I might remote onto it and try a few more things, but can't do that until after noonish.

I may also try to reinstall file and print sharing, see if that fixes anything.

Anyone have any ideas?

Update:
I'm also going to be checking local security policy to make sure auth users can access over the network.