clear the cache

You don't need to do anything to Windows 7 to make it work properly.

There are some things in Windows 7 that will never work properly and those things are not going to be fixed :-(

If you want to remove some temporary files, use these steps:
Disk Cleanup - Open and Use
But you probably will not see any performance gain.
Your antivirus scans might go a tiny bit faster if temp files are removed.

What cache are you referring to? Windows 7 has several.