Depends on your iMac model and OS version. If you are really running OS 8.6 or earlier, we need to get your post moved to the forum fro pre-2006 iMacs.
Most wireless USB adaptors require a minimum Mac OS of 10.3.9. And most such adaptors on a store shelf won;t work on Macs because they lack proper drivers. You usually have to web-order to get the right device.
If you clarify which iMac variant you have, we can offer more help. Doping "About this Mac from your Apple menu is a great place to find the Processor type and OS version.
The wireless adapter would be an Airport Card. Your vintage
iMac most likely has a slot for one. The card will relate
to a wireless router such as Airport Express, or Airport
Extreme. Once you update the OS to the latest version
possible make sure you have the latest Airport software
- this will help you set up the router more easily than
Sounds like a nice little vintage rig. All best, Tom
Tom, He may be out of luck. I dug though the specs in the MacTracker database before I posted and found the first CRT iMac that had slots for Airport cards already had OS 8.6 installed from the factory. He has 8.5.1, suggesting his is the 1Gen G3 version with a tray-loading optical drive and no accommodation for an Airport card.
If that's the case, his only wireless option requires three steps:
- upgrade to Panther--not easy as proper disks are hard to find and expensive
- add RAM to at least a total of 256MB to make Panther doable
- get a Mac-compatible USB wireless adaptor.
The total cost could be US$100-200 depending on what kind of deal he can get on the OS disks.
An alternative solution, albeit not USB, could be to use a wireless Ethernet bridge (sometimes called gaming adapter) connected to the Ethernet port of the computer. These devices (such as the WET610N from Linksys and the WNCE2001 from Netgear) do not require special driver software, and can thus be used under older operating systems.