Cannot Acquire DHCP Address Only APIPA?

I have 2 computers that cannot/will not acquire an IP address from my DLink router.There are 2 other computers that aren't having any problem at all...so I assume that it is not a problem with the DHCP service of the router. The 2 computers are laptops: one netbook running Windows XP and another standard laptop running Windows Vista Home Premium x86. Both computers are running McAfee and I have scanned with McAfee and Malwarebytes, and both are malware-free (no infections were found on either system on first scans...so it's not like I'm dealing with a system that has had infections removed). When connected to the network, they attempt to acquire an IP address, but cannot for some reason and then Automatic Private IP Addressing takes over and they come up with a 169.254.x.x address. I cannot figure out why this takes place, as I have gone through Winsock repair, uninstalled and reinstalled both network adapters (ethernet and WLAN) on both laptops and nothing seems to make a difference. I have even tried disabling APIPA by adding the "IPAutoconfigurationEnabled" DWORD value in the registry......still the same. I have manually configured the adapters with a static 192.168.0.x address, and I can begin to communicate on the local area level...but still cannot establish any kind of Internet connection.