Computer locks up if internet dies. HELP!!!

[Richlife]

Hi everybody. My girlfriend's computer freezes and has to be manually restarted each time the internet goes out on it.

It's an older model, an I notice a similar things happens on my laptop.

Both are using wireless networking and on both of them the Linksys program that finds the internet runs very slow and often crashes on it's own. Any help?

She's got:

WinXP
256MB Ram
Pentium 4
It's a linksys pci slot that has speed boost on it, i'm not sure the model or anything right now.