Apple – Support – Discussions – Every reboot Library is corrupted ….  Katrina S has the solution.

Some other software is probably conflicting with itunes saving its database.
As a workaround, start saving the ITL file in another folder before you restart your laptop. Create a new special folder just for this, something like C:\iTunesBackup. Better yet, put it on a USB thumb drive. After the reboot, you can copy it back to the correct place.
(side note: I back this file up weekly, more often if I have done a lot of additions/editing in itunes, and ALWAYS before an itunes update. I have 5 years of ratings, play counts, and play lists I do NOT want to lose)
Then it is up to you to find what software conflicts with itunes. Some programs posted here have been
IO bits
Windows Live One Care
ESET NOD
Symantec/Norton
Carbonite
Uniblue Speed up my PC

That is a short list. There are dozens of programs that could be doing this, and we don’t know what you have installed.

But basically, you need to tell whatever software it is, to not scan or monitor the itunes library ITL file or even this entire folder:

C:\Users\ username \Music\iTunes