Linksys pci card don't doesnt work

Hello,
I'm done talking to freaking at@t representatives and Linksys representatives feeling like i'm a messenger between the two. They say its this and that but i just found out something. I bought a wireless pci card (thats a linksys) and try to install it in my dell desktop (that running perfectly and is service pack 2) (practically clean). i install the card perfectly and correct, my computer reads it correctly and the card works but when i connect to my wireless network which it does read, im prompted to put in my network key(which i do) but it gets suck on "acquiring network signal" and thats it. The key is correct and EVERYTHING IS INSTALLED CORRECTLY. I tried EVERY TROUBLESHOOTING IDEAS FROM BOTH AT@T AND LINKSYS but none of them work. So just when i thought that the card was defective (as both told me) i installed it on my other desktop is running on xp pro service pack 3, it works like a freaking dream what am i gonna do? is it my computer? cuz once again i've tried everything. WHAT DO I DO? SOMEBODY PLZ HELP BEFORE I FREAKING THROW MY COMPUTER OUT THE WINDOW!!!!!!!!!!!!!!