x64 Vista, 32-bit XP, two workgroups

Hopefully the subject line says enough!

I am attempting to map a drive on a 32-bit install of XP (workgroup HOME) to a x64 install of Vista Business (workgroup OUT). The XP computer is the only 32-bit xp install that is on a different workgroup, and refuses to connect with x64 Vista. With 32, it was fine, but now? no-go.

How do I map this network drive?

Recap:
64-bit Vista
32-bit XP
Two Workgroups (cannot be changed as it will affect approx 15 PCs/Macs).

The "bitness" doesn't matter across the network, and workgroup membership is almost irrelevant in this context too.

I'd suggest you temporarily disable all software firewalls on the two machines in question while you're troubleshooting. Then:

1) Bring up a CMD prompt and test whether you can ping-by-IP in both directions.
2) Same for ping-by-other-machine-name.

If that fails, you've got network-level connectivity issues that have nothing to do with authentication or drive mapping. Otherwise...

3) Can you UNC to a valid share on the other machine? (start | run | \\OtherPCName\ValidShareName )

If that fails with an "access denied", try this on the XP box:

NET USE \\VistaName\IPC$ /u:VistaName\VistaAdminAccountName *

It'll ask you for a password. Obviously, type the password for the Vista account you specified. The response should be "command completed successfully" and you should then be able to browse the admin shares (C$, D$, E$ ...) on the Vista box using UNC syntax (\\VistaName\C$).

Otherwise, if you want to map a drive as a specific Vista user:

NET USE * \\VistaName\VistaShare /u:VistaName\VistaUser *

That tells it to make the connection in a particular user context.

the ping ip works, and I can see it, but the issue is becoming that I can't log on. It says that the password (everyone else uses to easily login) is incorrect!

Make you type the username & password exactly like you do to logon to the other computer. The whole thing is case-sensitive and beware of any spaces in front of or behind either the username or the password. And the computer you are logging onto has to have a password or you will not ever connect...