Take that laptop out of the refrigerator then it won't freeze :P or when it got friezed put in defrost of you microwave oven. It is as simple as it sounds :P  

As expected....sajha ko tori lahurey haru ko tori comment....anyway thnks for advice

Go to Windows Task Manager and check if any program is using heavy memory it would be better to keep eye on memory usages and close unnecessary Programs frequently .

What is your OS?
What is the Ram?
What the hard drive you have and what kinds of software you have downloaded, Do you have anti-virus a d internet security ?

What type of laptop you using and the specs?  If you give these infos along with your problem someone might be able to pinpoint the problem and give you right suggestion otherwise you may get funny comments ( overlook them).

Virus , not enough ram to run programs, overheat will make your computer freeze.
( Are you a DV winner? )

Hmm, it sounds like a hardware problem. Check your harddisk (defragment all the drives).

If you still cannot figure out why and you have about 1-2 hrs on your hands.

LOL DD bro but great advice.

DD's suggestion is the best :). Espically the last one.

I am adding few more

1. before restoring, try defragmenting the hdd. (start/all programs/accessories/system utilities/disk defragment)

2. Be careful if you are using registry mechanics/repairs. Not all the time your registry will be fixed properly.

3. If your computer boots well ( without slowing) , you can use Avira antivir, that is free and scan your system. ( if it takes forever to boot, use avast)

4. If it detects and repairs lots of virus, you may wanna reinstall the os or recover to the original /factory condition. Follow DD's guidelines up to 8.

5. Dont forget to check which processes/programs is eating up your big chunk of  resources. Kill em if needed.

6. I personally dont think this is overheat problem as your system temporarily freezes but doesnot shuts down ( if i understood it correctly).

If this fixes your computer, strictly follow DD's guideline #9.

Thanks all of you for advice....all of your tips were helpful...and I also upgraded ram...now its running good.....and porno is streaming very good :D..