No connection with added older compaq

Hello,

I bought an older Compaq EVO and just for a few school things(I am a mac person) had some upgrades done, memory, DVD drive and refurbished cisco flash drive for wireless. OS is XP. My wireless router (Netgear WNDR3300) works fine at home with my macs. The compaq worked fine in the computer repair shop with their wireless. Will not work at home with mine. I have input all settings with correct security, and it thinks there's no flash drive connected. So I bypassed that and tried it as not saving info to flash drive, but input manually, still doesn't work. I have reset the router. The compaq sees my network, just tries to connect and never does. I have $230 into this computer. Now it's black Friday and I can probably get a newer one for that same amount, but I hate to do that if this is something I can fix myself, but if I have to shell out more money for a tech to come to my house, maybe I should just buy a new cheap one? Thanks.