Unable to contact DHCP server

I'm hoping someone here can help me. I'm not a networking person by
any means, but I've been able to set up my home network in the past. I
just upgraded to a Linksys WRT300N and I'm able to get both my laptops
on the network. However, my desktop fails to obtain and IP address. I
get the message "An error occurred while renewing interface Wireless
Network Connection : unable to contact your DHCP server. Request has
timed out."

I've read countless forum posts about winsock corruption or
reinstalling TCP/IP protocol. All of this sounds extreme and I don't
know enough about windows or networking to feel comfortable doing any
of it.

Does anybody have any experience with this type of error? My desktop
is running windows XP SP2. My card is a Trendnet TEW423PI 54Mbps
802.11g. My router is set to BG-mix, WPA, and Wireless MAC filter is
disabled. I've also tried netsh reset which didn't work.

Thanks!