Sharing a drive - access denied

Hello all!

I'm having a problem that I think a lot of others are having, but I haven't
been able to find the solution to it on here or the rest of the web.

I have two additional drives besides C: in my desktop computer which I have
given the letters of X: and R:. I use these to store my small business
information. I then have a laptop that connects wirelessly. Both the desktop
and the laptop are running Vista Home Premium (both computers are less than
2 weeks old).

I have tried sharing the X: and R: drives and have given "Everyone" full
permission on both drives, but I'm still getting the same "Access is denied"
error message as mentioned in other posts.

I have Trend Micro Internet Security 2007 as my firewall, but I get the same
error regardless of whether the firewall is enabled, disabled or the program
has completely exited. I seem to be able to share individual folders, but
these two drives have hundreds of folders that I need access to. I can't
share individual ones.

Please help! This is extremely frustrating as something like this used to
work so easily under Windows 2000 or XP. If the solution has already been
found, please point me to the information I need or please step me through
what I need to do to get this working.

Chris