First:

H/W Diagnostics:
Please start by running these hardware diagnostics:
Memory Diagnostics (read the details at the link)
HD Diagnostic (read the details at the link)

Also, please run one of these free, independent online malware scans to ensure that your current protection hasn't been compromised: Malware (read the details at the link)

Next:

Upload Dump Files:
Please go to C:\Windows\Minidump and zip up the contents of the folder. Then upload/attach the .zip file with your next post.
{Left click on the first minidump file.
Hold down the "Shift" key and left click on the last minidump file.
Right click on the blue highlighted area and select "Send to"
Select "Compressed (zipped) folder" and note where the folder is saved.
Upload that .zip file with your next post.

If you have issues with "Access Denied" errors, try copying the files to your desktop and zipping them up from there. If it still won't let you zip them up, post back for further advice.

If you don't have anything in that folder, please check in C:\Windows for a file named MEMORY.DMP. If you find it, zip it up and upload it to a free file hosting service - then post the link to it.
Then, follow the directions here to set your system for Minidumps (much smaller than the MEMORY.DMP file): Set MiniDump

Did you run the Hard Drive diagnostics? If so, what were the results?

Try this in order to get us some information:

MSINFO32:
Please go to Start and type in "msinfo32.exe" (without the quotes) and press Enter
Save the report as an .nfo file, then zip up the .nfo file and upload/attach the .zip file with your next post.

If you're having difficulties with the format, please open an elevated (Run as administrator) Command Prompt and type "msinfo32 /nfo C:\Users\Public\Desktop\TEST.NFO" (without the quotes) and press Enter. Then navigate to the C:\Users\Public\Desktop directory to retrieve the TEST.NFO file. If you have difficulties with making this work, please post back.

Was the Registry optimizer a cleaner? IF it was you may have deleted important registry files from your system, causing crashes.

Are your drivers up to date on your hardware? Yes it is a long shot but sometimes bad drivers would cause a crash, especially after using a registry cleaner.

Sicne you said you have a virus...u should reformat and redo the system. It may say that it is gone but the damage is done. A "virus" is never destroyed, you can only treat the syptoms, but never the virus itself.

Hope this helps.