my laptop has gone very slow , my cpu usage is very high more than 50 %?

there still is a program or a short somewhere using most of your resources. this could be a browser, spyware program, word processor, antivirus program, etc. even when you reformatted your hd. you definitely need more ram especially if you are trying to run a OS like w7 which requires a minimum of 512mb ram to run but runs better with 1.5gb ram or better. i would us an older OS like xp and also use older word processor like Microsoft office 2000. I have xp, have a dell d600 with 512 ram which is older than your laptop and it runs fine with xp and office 2000.

There are 3 effective steps for you to solve high cpu usage problem.

high CPU usage was a serious problem in the computer and it caused Blue Screen of Death. I felt disappointed about that for a long time. Fortunately, I fixed high cpu usage by using some useful tips. high CPU Usage is usually caused when the Operating System's registry contains errors or some Windows files are missing. If your computer got high cpu usage problem, that means your computer is in big trouble. You should immediately fix it. There are so many ways for you to repair high cpu usage problem. According to my experience, you could try the most effective one below:

Step 1: Download and install a high cpu usage problem repair tool such as Registry Easy

Step 2: Click the "Scan Now" button. It will full scan your PC for Free

Step 3: Click "Repair" button to automatically repair high cpu usage problem for you.