PC 1 Win XP Pro latest updates
PC 2 Win XP pro latest updates
PC 3 Vista Ultimate latest updates

PC1 has a shared drive.
PC3 Vista can see it and access it.
PC 2 will not see it at all.
All firewalls are off on PC2.
PC2 sees workgroup of PC1 (but not folders) and PC3 (no shared folders)
All PCs have different workgroups

All PCs access the internet OK
When I try to map PC1 from PC2 it fails.

What is going on?