Signal quality is typically more of a barometer of your wireless connection than signal strength actually. Unfortunately XP's utility doesn't give you this number. Certainly if your strength is poor your pings are probably going to suffer but you could have superior signal strength numbers but if your signal to noise ratio (SNR), which is usually listed as signal "quality", is bad, then your assocation to the AP is going to be crap. The easy things to try are switching the frequency base (channel in budget/consumer AP speak), moving the antenna as suggested if possible, and moving the Access Point itself. If it is crammed into a corner your problem very possibly could be solved by getting it out of a corner and into open space. Even with diversity (spatial) antennas, which you'd probably have if you have more than one antenna, can often not overcome severe multipath environments. And a tight corner certainly qualifies for that description.