my system is an old one
IBM 2.6 Ghz
512 ram
40 hard
it was doing just fine but from some time it runs slow like when i minimize a window or close it, it drops like a water fall slowelly and some times it litterelly halts and shows a massage “windows explorer not responding”
it happens specially when i use fire fox
any idea what,s wrong
i know it,s not a registry problem then what?
You could do all those things and it may help (cleaning up the disk and registry, doing a defrag or reinstalling) but I would try turning off Windows animated effects. 
Reinstall your windows simple solution for these types of problems.
Have you scanned for adware, viruses, etc…?
Do you have Winzip installed?
It’s probably the system that is short of memory and having issues running several hungry programs all at once resulting in lag, etc. You may also want to do the usual like clean-up the system clutter, etc.