I do apologize for getting your set up wrong. That's what I get trying to work and do G2G at the same time
Let me recap and see if I understand:
You have a desktop with Belkin wireless card - it can not connect all of a sudden.
You have another dekstop with a standard ethernet cable connection that connects fine.
You installed another wireless card on an xbox that would not connect - had to run cable for the card. ** Is this the Linksys card?
Your daughter's laptop connected fine on a wireless connection.
Is that accurate?
If your daughter's laptop can connect wireless on your router, then the router's okay.
The Belkin card had been working then just quit. They do die sometimes. But also check for any configuration changes to your firewall and/or antivirus software. It's possible some update has changed something important.
Did anything else change on that computer the day before the Belkin card quit working? Did you install anything new, software, hardward, or any kind of updates?
Two other things to try, to rule out software conflicts:
1. Do a Windows XP System Restore to the day prior to the Belkin card quitting. To do a System Restore, click Start, All Programs, Accessories, System Tools, System Restore. Follow the prompts.
2. Boot into Safe Mode with Networking. While starting your computer tap the F8 key once every second during the memory count up, or during the system spash screen where you see the system maker's name (HP, COMPAQ, DELL....etc.). This will result in a text based menu. Use the curors/arrorw keys to navigate to SAFE MODE WITH NETWORKING and hit enter.
Does the Belkin card work in either of these situations?
I'm not clear on where the Linksys card was installed. Please clarify.