My Advent 4211 netbook connects wirelessly to the Internet through my Desktop and a Belkin router. How do I allow the netbook to see the files in the desktop?

If you ran your network wizard to get the internet access shared then you should be able to share your files too.
and folders the same way ,

go to my network device,
veiw network computers,
if you can see the computers desk top then
go to Shared folders and try to see if your folders have been shared open something.

If you can see the desktop and not open the shared folders then run the network wizard again,shutdown and restart,to save your settings,
to share files between both machines you will need to drag the file into my shared folders or rightclick on the file your sharing and click on sharing,follow the prompts to share and that should fix your problem.

Please rate me thanks MISTERDJ