mainboard won't give memory range to PCI card

I had to setup a wireless network; I usually stick to ethernet cabling.
Go through box of spare parts. Tried a D-link card, but Windows 7 does
not support it. Apparently particular card will flip out to the BSOD
if you force to use older XP/Vista drivers.
Then try a TP-LINK, what is Win7 compatible. But Win7 will not configure it.
Go into device manager, and it tells me I should update BIOS. Resources
show the desired memory range is not available.
Now this mainboard gives 3.5 GiB usable RAM. Most mainboards have 3.25 GiB
free in a 32-bit Windows. I have not seen one before that got away with
3.5 GiB. I believe with Intel FSB chipsets, 0.5 GiB was the utter minimum
you could lose.
I looked up the BIOS updates, and was only one later for newer CPU support.
Anyway, as it is a Core 2 system, I decided to retire it to the dusty
space under the stairs. It was a "budget" board, only 2 PCI slots and no
firewire or eSATA. Just curious it will not donate some memory range to
another card.