See is this helps: Microsoft Vista Home Networking Setup and Options

i have been able to access the files on my XP computer from my vista laptop, but am unable to access the vista laptop from my XP desktop.
in xp from 'my network places'=> 'view workgroup computers' i can see 'Dell-pc', but when i try to access it a window prompting for the user name and password appears. when i enter the user name and password that i use for my laptop, nothing happens. the same window appears and nothing happens.
where is things going wrong. can anyone suggest

Hmmm, I don't know but my guess would be a firewall issue - the Vista machine is not allowing access.

i was able to access the vista machine after disabling the 'password protected sharing' in the "Network and sharing center" of windows vista.