Windows 7: Not geniune - Trying to remedy with purchased OS

I am getting the "Not Geniune" message. Most likely it truly isn't geniune, as a friend gave it to me when he went to Mac.

However, I went out and bought the same version, Windows 7 ultimate x64 from NewEgg. Is there a way to "cure" my existing install, using the newly purchased software, without having to wipe it out completely? I don't have a lot on here yet, but, would save me the time nonetheless.

Quick assistance much appreciated.

If you could or could not is not important, uninstall and install lthe genuine one. If it is a countefeit you do not know whats in it.
Virus
Tracking software
Who knows
Do it the long way now to save time later.
If you had a qualifyin OS before the non genuine install, you can and should make a clean install with format. In your case the format is very important.
YOu will reinstall programs etc after the install.

You can run a Repair Install.

Repair Install

That will fix tampered licensing files and any other "customizations". Before running the repair install, also see if you can figure out what cracks/activators were used and uninstall them manually, Google is your friend.

If you want just change the key, you can do so at Computer>Properties.

If no option shows there to Change Key, then open an elevated Command Line, type:

slmgr -ipk xxxxx-xxxxx-xxxxx-xxxxx-xxxxx (insert Product key in place of xxxx's)

If the licensing files are messed, simply changing the key will not work.

Dont you think that with a cracked copy its best to start fresh? There may be more on that OS than windows.

A crack is a crack, its not malware in the traditional sense. All it does is alter some files that fools the system into thinking the copy of windows is genuine. So its quite possible to repair those files and get going.

I wouldn't chance it, but then again I am extremely anal about my Windows install. Just start clean and never look back.

So it would need a Repair Install at the minimum to repair files added by the crack?

What about possible changes made to the boot sector? Should the HD be zeroed as a precaution?

Personally that is how I do any install, normally a secure erase with parted magic. It may be overkill but I like to start with a clean disk.