I've gotta add a note in case it helps even one poor soul.
First and foremost, don't assume your data is "lost" -- even if the PC vendor says it is.
Try a product called "Restorer2000" -- I have used it for several years with good success.
I do software development and "trashed" my registry. HP said my only option was to restore using their recovery utility, so I backed up all data to my second hard drive. After their utility ran, I noticed the C:\ drive looked just like the D:\ drive (I forgot to unplug!). Their utility formatted and installed XP on BOTH drives. When I called HP, they said "your data is gone and there is no way to recover..."
After testing a few recovery products, I was able to recover over 95% of my data! (Since I frequently reimage my machine, I install ALL products, then restore a backup of all data files. Since the data always goes on last and their restor doesn't put any 3rd-party software on the system, their image is always smaller, thus low risk of writing over my data.)
If you THINK you have lost your data, DO NOT do anything that will possibly write over your now-hidden data. i.e. do not install recovery software on that disk! Take your hard drive to another machine (as a secondary drive) to recover.
Bad advice from vendors is not unusual, so be wary and get a second opinion first (kinda like when HP told me I had "damaged" my hardware by installing software and would need to ship the pc back to them for repairs!)
Good Luck to ALL!
"Have a great day today and a better day tomorrow!