[monkey]

Well I disabled most of the items from the startup menu but it didn't help much. I checked HDD for errors using Western Digital tool but again no solution. So I ended up using Western Digital Data Lifeguard Tools which made some changes to registry. After this there was gud improvement in the start-up time. I re-installed everything back (with items being added to the start-up menu) and the performance is much better now. I will use the system for a day or two before confirming if the problem has been solved.

@ilugd: If you have genuine full license of Ad-Aware then you will have to get new Key everytime the software is installed after formatting. The license is based on Hardware-Print of your computer and this Print changes everytime the Windows is reinstalled.