Alright when it is Vista and Xp then normally you would have a problem as Vista won't make the OS backwards compatible.
You will have to make sure that both computer are in the same workgroup.
Here is how you do it: Press the winkey+pause break and go to computername.
This is a winkey:
This is the screen where you can change the workgroup:
Here you have to click on the change button.
Then you get this screen:
There you have to click at the workgroup and give it a name then just click OK.
You'll get a screen saying:"Welcome to the ... Workgroup."
This will be slightly different for Vista.
I hope this has helped you.
Oh you might want to check this topic.
http://www.computerhope.com/forum/index.php/topic,37459.0.htmlIts how you can share printers and folders with Vista and XP.
Witch version of XP and Vista are you running? Like home or Home Premium. Type "Winver" (for XP in: Start -> run) (For Vista in: Start Search bar)
If you need more info just let us know.
Jonas