Depends on what kind of Wireless Adapter you are using
There's the Wireless Adapter Card
Comes in three styles of connection,
1) PCI Wireless Adapter Card,http://www.tigerdirect.com/applications/SearchTools/item-details.asp?EdpNo=4389486&CatId=2701
2) And PCI-Express x1 Wireless Adapter Card,http://www.tigerdirect.com/applications/SearchTools/item-details.asp?EdpNo=1068811&CatId=2688
PCI-Express x4 style may be out there too.
(I've never bothered to look. I use the USB style)
A Wireless Adapter Card based on the PCI technology, goes in a PCI slot. Generally White in color, but NOT always,http://en.wikipedia.org/wiki/PCI_local_bushttp://en.wikipedia.org/wiki/File:PCI_Slots_Digon3.JPG
A Wireless Adapter Card based on the PCI Express technology, is used in a PCI-Express x1 slot, http://en.wikipedia.org/wiki/PCI_Expresshttp://en.wikipedia.org/wiki/File:PCIExpress.jpg
Top example is a PCI-Express x4 slot.
Moving down, next is a PCI-E x16 slot
Next, PCI-E x1 slot
Next is a PCI-E x16 slot,
and the last one at the bottom is a PCI slot.
Notice they are all Yellow.
Color of connector does NOT matter.
What the expansion slot is, does........
Also there is a USB Wireless Adapter,http://www.tigerdirect.com/applications/SearchTools/item-details.asp?EdpNo=3970955&CatId=2704
This type of Wireless Adapter, plugs into any available USB port on the computer.
Front or back of an eMachines desktop computer, in any available USB port.
Any available open USB port, on an eMachines laptop.
(Or any computer manufacturer)
What is the model number of the eMachines Desktop PC?
Examples, T1090, T2460, W4685, D2246, etc.
I should be able to tell you what motherboard is used inside, and may have access to a link, to the Motherboard Manual.
Post back in a Comment.