Has my computer been hijacked?

This is my first post, so if I inadvertantly screw up any protocols, my apologies in advance.

I'm hoping someone can give me some advice on this....
I'm running XP with a 2.6G processor and 512meg of RAM and have plenty of space left on my HD. I have current Norton Internet Security and AV programs with automatic Live update, and I have automatic Window security updates, too. I have a cable modem and leave the computer on. Last Wednesday I saw (didn't read thoroughly) an article online regarding some possible problems with Russian hackers and Symantec Live Update. That evening I tried to manually run Live Update and I received an error message saying it wasn't available. I tried the next day with the same results.

My daughter told me this morning, Sunday 6/27, that the computer "was acting funny." She and a girlfriend were up all night IMing friends (a normal deal) and she swears they didn't open any e-mail attachments or click on links in IMs, and I pretty much believe them. These are the symptoms:

1) Norton AV won't run - it appears to be disabled. I can get it to run off the CD when it boots up, but it's a 2003 version and while the results of that scan says no infections, it doesn't have the benefit of the newer definitions.

2) While I can access the Symantec and McAfee sites, it will not allow me to run their web-based virus scans - other hyperlinks work, but not the scans.

3) I get a "Symantec Settings Alert" advising me I might be subject to a remote attack after booting up, and it suggests I uninstall and reinstall their product - unfortunately, when I attempt to do this, I get an error message advising me "Windows Installer Service could not be accessed" - looks like this has been disabled, too.

4) When I attempt to use the Search all Files and Folders option in Explorer, this single hyperlink has been disabled.

5) I took the computer offline and opened the task manager. I noticed that the file svchost.exe is expanding by about 10K a second. There is another file of the same name that doesn't increase at all.

Ant suggestions? Thanks!

 

Try an online scan antivirus scan from Trend Micro or Panda. I believe that both offer such services. Sorry that I can't provide a link to them.