For everyone out there who might have this problem.
We all know you're getting the error since you're using a pirated version of XP - I'm not gonna be a wussy who calls you a thief and refuses to help you since we all have our reasons to pirate XP, and some of them might even be legitimate.
The crack you used is probably the same one everyone else who is having this problem used. The issue arises since the crack changes the winlogon.exe file to give you an error if not activated, and not let you logon. You applied the crack after a fresh install of XP. Works great. Then, updates come along and SP2 changes the winlogon.exe. All you need to do is crack it again.
I didn't do that, and I waited until day 0. I couldn't log in to my user even through safe mode to recrack it, like some people were able to do. I tried repairing my XP installation, and that downgraded me to SP2 since I used a SP1 disc, but it didn't remove my activation information. I was in a pickle. I had my own and my other user on this computers data locked away.
Luckily, I had set aside a partition for Ubuntu that I never installed since I'm lazy. I used that partition to install XP again, then ran the crack from that user but browsed my winlogon.exe in the WINDOWS folder somewhere in the other disc, and cracked it. That saved me having to backup everything and reinstall xp. Phew.
I hope that helps some people, although you kinda need to have a partition to do that. Otherwise, I hope it lets you know you need to re-crack it before day 0! I looked all over the interwebs for this solution, and none fit my situation. Spread the knowledge!