Why would Windows XP Pro stop file sharing by itself and say that all usernames and passwords are incorrrect when they are correct, and how would I fix this?

It is because it is Windows XP and there is no way to fix it as such.

Usernames and passwords are incorrect? In regards to what? Messenger or Windows logon or something else?

Windows logon... but shouldnt matter as it uses the same uname and pass on each comp.

I'm not following you now, is this file sharing a network thing? the shared documents type folders (I know you can set more folders as shared)?

Yes those type, none work

I guess the first thing to check is the workgroup correct? I had loads of problems with them, gave up eventually.

Yes.

Accept that Sharing Folders is critically flawed and move on.

I'm afraid I have to agree with Aaron, as I've said, my sharing folders haven't worked for ages, even if I set up the network again.

Sometimes, my sharing folders refuse to share because of an "Unknown error". I don't know why this happens...

Are you talking WLM aaron, cos I'm on about \\machine\share

I had that problem before.

Resolved by adding my IP address range in to the trusted zone in my firewall application.

Ok well that doesn't help me because its already trusted... and now when typing \\compname all it allows me to try is compname\Guest... I'm not running XP Home it shouldnt be doing this :@

Have you tried doing it without passwords?

Yes, still nothing :/

Well, when I had that problem I recreated the network from scratch. It kinda worked, kinda didn't. If it's important, it might be worth a shot.

I had a problem which sounds like yours, although you've probably already tried this. It would not let me connect to my brother's pc (or vice-versa) unless we each had at least two users on the pc. Having just one would not work.

/advice from a noob

I know this is a bit deep. But do you have a shared drive on one of the PC's trying to connect to the other one with a bad username or password, or do you have a service running on one of the PC's using credentials from the other PC that are incorrect? As this could lock you out of the other PC.

Just do a quick net use and see what's in there. Some shared drives are hidden you see.

Make sure your user accounts have passwords otherwise it makes sharing really difficult. Also, make sure sharing permissions are set correctly.

Right update on this.

It's still not working, nothings connecting to it, nothing will connect to it, and I think I might just reinstall windows this weekend lol

Good idea