Specification of the PC, PC Specification, PC Spec, i'm not sure how else to ask that?! All I was getting at was that when you're wired, there's no encryption taking place, when you're wireless you have encryption. If the processor is a cruddy old one then it's possible that the processor was an overhead. In your case, it's not.
Right, so back to the earlier question, have you tried the same speed test with all the encryption turned off anyway? It could be that the access point is processor bound. I haven't done any throughput tests on that router.