I had an old "pen" addaptor and it was actually pretty good. Dad got one with his router that sets on the table and it has MUCH better reception than my internal wifi card. So, I'm sure it all depends on what brand/model/surroundings there are...
If you must get a wifi card for your desktop, I'd reccomend a PCI card. But, from my experience with the USB one, they are good too.
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Urban De-Development
* Athlon X2 4200 | 2048M RAM | 160G HD | 7600GT
* C2D T5250 | 2048M RAM | 160G HD | Intel x3100
* G4 1.33GHz | 512M RAM | 40G HD | Radeon 9200
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