Windows 7 problem

first of all, are your system is up to run the windows 7 ?

How much RAM you got?

If you use an antivirus software, you may want to turn off the real-time scan or something like that.

When the windows 'overleads', ctrl alt del and see what's causing it.

overheating?

try malware bytes and hitman pro.

Check the defragmenting schedule, maybe it's that.

Maybe related to some faulty driver or the drive needs a defrag?

list all your hardware and maybe we can get the picture of the problem, also programs you use the are currently running after starting windows.

What stuff you have running in background?

I have a system optimization application, which really oprimizes speed as it should, which sometimes after system being idle for some time starts to run some cleaning operations which slow down the system, so you can have some antivirus or some stuff like that as well.