Windows Vista forum: how do I fix a corrupt registry

My desk top computer ... Asus p5ld2 MB, Pentium d 2.8 ghz dual core cpu, seagate 500gb sata HD - 2 partitions, asus EAH4350 Video card, 3 GB DDR2 pc4200 ramm, 650 wat PS, Windows vista home premium ..... built in 2009 .. been working great till now ...
History .... have done all windows updates as they came out, have not added anything new in quite awhile, have redone cpu thermal paste with artic silver within las couple months as cpu was overheating, am now running asus probe to monitor temps, cpu still get to 60C and MB to 46C when using computer under medium load ... I do not do games!!! ...... I have been building and working on computers for me and family for 17 years, so I have a decent knowledge of computers, but definitely not in depth when it comes to digging into windows files or registery.

Problem.... started 2 days ago, noticed it was running sluggish, programs would not respond, would need to wait a couple mins before they would respond ... System shut down, restarted, was still not acting normal, slower then normal, finally became non-responsive and shut down ... It then would not boot up, said could not find hard drive or OS . will not boot in any of the choices shown when I hit f8 at startup, have tried all of them with no success.. I put vista dvd in and ran repair and it repaired the MBR, but now it says the registry is corrupt and windows cant repair it. I have had the good sense to turn on system restore and make sure it does a restore point every couple weeks, and have done backups onto a thumb drive of all my personal files along with windows system files just in case this happens. When I try to do a restore from windows dvd repair, it says there are no restore points, but I know there are plenty. I dont know if I want to do a complete PC restore as Im not for sure what it does and if I even have the proper backup file to do it.

My questions ... is there a way to retsore my regisrty with the system restore even when its saying there are no restore points, but I know there should be?? Also, is there a way to restore the registry from the backup that I did on the thumb drive?? The part of IT tech I am not is doing commands at the command prompt, so if it involves this, I will need very clear instructions and step by step also. I am sure there is a way to do this without wiping the hardrdive and starting over, but here is where my knowledge fails me. But I can do anything with good instructions. If someone has a link to a site that will educate me in this kind of IT tech information, I will read it and save it for future trouble shooting. But it has to be somewhat of "command prompt commands 101" so I can understand it. lol .