Vista - File Sharing Help, Please!!

Hi, I have a Windows XP Home Edition desktop and a Windows 64-bit Vista laptop. I am trying to connect to the wireless network we have established. The connection works fine to access the internet from the laptop (the desktop is connected by Ethernet), but I cannot access our external hard drive (attached by USB to the desktop) or shared folders that are on the desktop. However, I can access the Shared folders ("Public") on the laptop from the desktop. Please help!

I tried:
-changing something in the registry from 1 to 0 (it already was a 0) - I don't remember what this was, but if your suggestion has to do with changing something in the registry, I tried it
-making the work group the same on both computers
-downloading a packet for Vista that was supposedly going to allow me to connect to the XP - somehow my 4 GB laptop didn't "have enough space" for the file
-toying with the firewalls (Trend Micro Internet Security with Windows Firewall on the Vista and CA Personal Firewall with Windows Firewall on the desktop) - even with both off, the connection still won't work
-a lot of other 'solutions' so please excuse me in advance if I snap at you for your suggestion - I'm just frustrated beyond belief!

Thanks so much for your help in advance!!


SOLVED:
Vista can't see XP - LLTD download rejected by SP3 - Tech Support Guy Forums

or

Link Layer Topology Discovery (KB922120) not included in SP3 no problem!!! Read on... - Windows Live

with turning my firewalls off and restarting after I did that - finally worked for me!!