Windows 7: Loading default profile (urgent help needed)

Windows 7 64 bit .... sp1
Yesterday I went to use PC and it said 'preparing desktop' and created a default profile.
I did a sytem restore back 24 Hrs ... and it recoverred and worked fine.
Today it's back again, tried restore to same point ... no fix, tried an earlier restore - same problem.

I did a google and found issue related to switch users (which we do use)
Windows 7 user profile lost when you log off or reboot

but there is no .bak profile there only the correct named profiles.

My profile is admin ...

Also noticed that if I look under "my computer" my D drive (Apps & data) is missing ... looked underthe accounts for 2 other users ... they have correct desktoips ... but they aslo can't see D:\

Not sure if that measn I have lost my HDD (OS is on sepearte C:\ SSD)
In case it's relevant ... when I switch on it boots to normal 'select user' icons ... and accepts user passwords.

Hi,

I would suggest to run Hardware Diagnostics on your computer. If there are no errors, then try restoring system back to factory settings and then check the performance of the system. Ensure backing up your data before reinstalling Operating system.