Wifi card not as good on one PC vs another

I swapped out my PCs. I had a cheapie home computer HP and upgraded to a HP workstation. The workstation does not come in with all the junky built-in stuff, so i did take the wifi card from the old computer and put into the new.

The workstation now drops connectivity to the AP frequently -- every few minutes. So I then tried a new wifi card, it was worse (couldnt even pick up a signal)

so this led me to believe maybe i had a weak signal to the AP .. so i bought the hawking hi-gain HSB2, put it on each AP and on the workstation. this helps a lot, now it only drops the signal maybe every hour.. but since my lifeblood is networking, it is tough to work like this when it drops every 30 or 90 minutes (inconsistent)

so here is my question: how can the PC dictate the performance of the network card? i mean it is the wifi card that should dictate how well it performs. why did the crappy HP do well and this high end HP not? what network card can i buy that will possibly work better? i think i need to keep swapping network cards to find the right one. please help this is very frustrating

yes i am using the remote antenna. i guess the workstation has the metal case so maybe the cheapie was picking up the signal right at the electronics and not just the antenna..

the antenna is in the same location .. i guess i could see the fans and case making it a little weaker, but with the HSB2s this should be rock solid and still it drops every now and then...

i think i need to buy a real nice antenna (and maybe for the HSB2s also) and perhaps a better wifi card (if that even makes sense??)

can you recommend antennas i should buy or what i can do to help ?