The tool you'll probably need to use to correct that is either secpol.msc or gpedit.msc. I can't think right off the top of my head which settings in there but if you aren't connected to a domain and that's your error then I'm pretty sure the correction to be made is in there.

There's a number of viruses that do exactly as you described.

Did you take your computer to have viruses/spyware fixed?

Many times, viruses and spyware make changes to your system which affect how your computer functions. Virus scanners do not fix these problems, usually. Most companies (like Computer Doctor) don't care enough to fix or even warn you about this... But of course, it is difficult to spell out absolutely everything that can go wrong after every single repair for every single customer.

If you did not take it in for viruses / spyware, then you should definitely get yourself checked out by something like http://housecall.antivirus.com

You should still do a virus scan. This may be a sign you've gotten another virus. But here's how you might fix it.

• Start > Run > gpedit.msc
• Click 'Computer Configuration'
• Click 'Administrative Templates'
• Click 'Network'
• Click 'Network Connections'
• Click 'Windows Firewall'
• Click ''Standard Profile'
• Double click 'Windows Firewall: Protect all network connections'
• Change value to 'Enabled' and click Next.

The default is 'Not Configured', but I've seen entries in gpedit.msc that were enabled or disable, but the interface did not say so. You may also find a related option in User Configuration / Administrative Templates / Network / Network Connections and possibly anywhere else. If a virus did this, it is perfectly possible to create new gpedit entries that you and I would have no idea about. You just have to look around.

Are you logged in as Administrator? Do you have an Administrator account?

If you have XP Home, you can login as Administrator via Safe Mode and you should be able to access GPEDIT from there.

Alternatively in normal mode, you can press CTRL+ALT+DEL twice at the logon screen and you should be able to login as Administrator. To get there, you can logoff (Windows key + L).

Although I might assume any "Administrator" account cannot be filtered from gpedit.msc like this, there may be an option in GPEDIT and/or a key in the registry to deny access even to administrators (which would be silly). I'm not sure what it could be though, so try searching for such a thing.