There is nothing faster or easier. When you add the time you've spent already, to the time you will spend fooling around with half-solutions, starting over is a better bet in 99% of cases.
Important: Do a FULL DISK IMAGE copy first, so that you can selectively restore any files you actually wanted, later. And of course verify the backup before you re-install.
But don't waste your time trying to scrape the mud off a pig just so you can smear lipstick on it. The Windows installation on the drive is crap. Start over.
I say that as someone who has done many hundreds of installations of Windows in the past 10 years, both personal and professional, and who now runs the IT department at my company.
Of course, you might be in the 1% where there's something SO PRECIOUS in the existing installation that you can't copy it off somewhere, and can never reproduce it. But I doubt it.
The problem with that of course is reinstalling all the programs that you do actually need it’s not all junk on your pc. I did exactly what you did frequently and then discovered that Norton for example only allows a limited number of installations and I had to go out and pay for a new cd.