From your message it sounds like you want to either do explicit (manually select which files get transferred) file transfer, or end up with the remote hard drive mapped over the network.
You can do the first one, using many programs e.g. PC/Anywhere. PCA is also one of a number of progs that will give you remote control over the remote machine - very handy.
If you want to map the remote drive locally (the 2nd option) Windows can do that natively. Just set up the appropriate shares. The trouble is that everybody will be able to get in there also, so you need to look into good security, and there are lots of ways to do that, from not too complicated to horrendously complicated.
Either way, it will be pretty slow, and not much good for effectively increasing the size of your hard drive. Even transferring 1 gig will take hours.