Last Modified, which app

If the changes are frequently made, you can use this method
How to troubleshoot a problem by performing a clean boot in Windows Vista or in Windows 7
It is probably the AntiVirus or some type of maintenace software, which I am not in favor of. Computer maintenance is easy and should be done by manually.
It can be caused by a scheduled maintenance task. Look at the last date, then go to task manager and look for a time that coincides.

Sure Toobs, actually I think tht is your best bet.

Type task scheduler in search.
Once in task scheduler you will feel lost for a while, but then you will see a pane on the left with a few enteries. On the left of those enteries there is a little pyamid, click on the pyarmids to expand the tree. You will see exactly what I mean once there.
Then look at the different routines that are scheduled. There is system restore etc. Click on each to see the schedule in the middle pane. If one schedule conincides with your problem, that is the cause.
Look at the maintenace schedule. amd antivirus schedule for scans etc.
That is the most likely.

Have you played any of these songs in iTunes? AFIAK, iTunes has a play count that is stored on the files themselves.
I could be wrong I don't use iTunes.