Sudden Slow-Down

[lcdfly06]

For the past year or so of having Vista on my computer, I have had no problems whatsoever, but this morning, I tried opening the program Guitar Pro, which used to work fine on my computer, and the computer couldn't seem to open it...just sat there loading forever, so I tried restarting...now my computer takes about 20 minutes to fully boot up. Once it's fully booted up, most programs run flawlessly, but not all. Random programs like Spybot S&D and a few others will not open or run. I tried reinstalling Vista, but the computer will begin to boot from the Vista DVD and then just sits there loading indefinitely. A few days ago, I downloaded a registry fixing program trial, and it "fixed" a few registry programs, and I am wondering if it "fixed" something that should not have been changed. I honestly have no clue at this point, though, and unfortunately, I erased the program and can't remember which one I tried.

Any suggestions?

[not important]

I would lean toward the registry "fixing" software being the start of your problem. If you want to reinstall Vista I would zero the HDD and then reinstall.
If you want to try and save it, download and run malwarebytes.