I'm a bit surprised. I use a spectacularly cheap PCI adapter myself and it works better than most laptops -- if only because it has an external, sticky-outy, antenna whereas laptops have it embedded in the lid.
Try moving the computer or raising the router. It certainly helps to have the antenna hard against the wall nearest to the router-- mine navigates at least three walls and about 50 feet in a building with a steel frame and I 'enjoy' between 40% and 50% signal strength.
Try changing channels, because certain frequencies work better in different environments. If there are neighbouring wifi networks, move to a channel at least 5 stops away from strongest. Relocate cordless phone base, video sender away from computer or router.