Hi Mirrajay,
You're dad is correct in so much that you can share a drive on a Desktop PC over your home network and on other PC's Laptop that are connected to the same home network.
I haven't had a look at the link posted by tremula, however, at this stage there are a number of possible areas which are causing it to fail. Desktop Firewall, Laptop firewall and security settings. Also, you need to setup both machines to be on the same home network name - else they wont 'see' each other. Windows 7 does have some new functionality which makes sharing easier, however that also requires the other machine to have Windows7 as well. You'll need to do a little digging around to find information in order to make this work - it's one of those things which is fairly straightforward to setup when you're at the machines, but hard to type out in a message forum like this! You may also need to take a look at your router settings as well, just to add another area for you to look into!
Good luck!
Cheers, DtM! West London & Slough UK!