This is a different problem - we've seen it a few times already.
Normally, Vista creates a system of links on the partition where it's installed. For example. C:\Documents and Settings is not a real folder, it's only a link to C:\Users.
On your machine, however, the link most likely points to a different disk (for example X:\Users - and the drive X: either doesn't exist, or doesn't contain a folder called "Users").
I don't know how this situation may originate, maybe by copying/cloning the partitions somehow - but basically the problem is on your disk (on the other hand, it's not a critical problem if your OS is running - so if you can ignore these errors in avast! results, you can live with that I guess).
What 808tida posted, however, is different...
