When I check the "Users and Passwords" in the Control Panel, I see two new strange user accounts. They are "IUSR_STATION-2" and "IWAM_STATION-2". Station-2 is the name of my computer. When I click the Properties button, they are described as "Built-in account for anonymous access to Internet Information Services out of process applications", they belong to the guests group. I never created those acounts. I deleted them, but every time I reboot, they show up again.

My guess is, some spyware has found its way to my computer and created those accounts for hackers for later malicious acts. I don't know how to deal with it. I'm running Windows 2000 Pro, SP4. I have Zone Alarm firewall, Norton Antivirus, and Windows Defender Beta 2 running as well. This computer is networked with two other ones, and the other ones don't have this problem.

Can someone give me some advise? Thanks.

not sure what they are ,but you should disable the guest acct if you haven't allready done so .
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Actually, these accountsare automatically created by IIS, the Web Server which ships with Windows. If you don't use a web server on your machine, you can uninstall IIS from Add/Remove Programs>Add/Remove Windows Components. Once you've removed IIS, the accounts will be deleted.