Windows 7: PC hanging up after installation of Windows

Hi, after installing the genuine pack of Windows 7 Ultimate 32 bit version my desktop PC performance slows down after sometime with slow videos and music, hanging up every now and then. Also the CPU and RAM meter given by Windows 7 ultimate shows RAM usage at 70-80% and processor at 100%. PC configuration: Gigabyte 8I945GZME-RH motherboard, 2.80 gigahertz Intel Pentium D, 16 kilobyte primary memory cache, 2048 kilobyte secondary memory cache, Board: Bus Clock: 200 megahertz, BIOS: Award Software International, Inc. F8 01/10/2007, ST380211AS [Hard drive] (79.88 GB), 1016 Megabytes Installed Memory, Realtek High Definition Audio, on board sound and graphics. No additional cards installed. The installation was a clean install. Any solutions?

Was this an upgrade or a "clean" install"

Most all of us agree that an upgrade is not the route to take. It leaves useless files on your system and can cause conflicts while you're e now.experiencing now

Save all you Documents, Pictures, contacts, videos, music, etc to a flash drive,

Be aware, you will need to re-install your 3rd party applications.

There i poll going on now and "clean" install is winning by a mile,.