Hi,
You need to give a bit more information as to what you might have changed or installed. You could boot into safe mode and note the processes running and then boot into normal Windows and do a comparism.

Avast is good, i use it myself so it does detect most virus signatures

Thanks for your concerned and contribution. . It displays not responding with the error warning "LSASS.EXE".
I first notice the problem when trying to copy an audio cd to windows media library.

Try doin a SYSTEM RESTORE, hope it works

Hmm, ,
LSASS is a Windows component shown in error messages, often due to a virus infection such as Sasser. It exploits a recently patched vulnerability in lsass.exe. major infections would cause your computer to shut down in 60 seconds. but u didnt mention dat. wot u can do is copy the error message and past it in a google search. you'll surely get som helpful results.

tell me ur progress,

Try going to StartUp >> Run >> Type in MSCONFIG, When the Box shows up, Under GENERAL tAB, select Normal Start up, SELECT the Start UP tab and then click to Disable ALL and then Click apply and then OK, Allow the system to restart and if things improve, it could be that you have way too many start up programs enabled on your system and you may need to basically disable some or delete what you do not need to be running on your machine at all.

You could start by getting a good antivirus program like Kaspersky or Eset NOD32. A good numbers of worms and spyware imitate the names of standard Windows processes like LSASS.EXE and SVCHOST.EXE and your Avast may not be able to detect them.