1. Uninstall Unnecessary Programs and games from the system
2. First of all u can unnecessary startup programs on the rigt side of the taskbar. because it can take long time to load.
Process: click State menu-->Run-->and type "MSCONFIG" after typing a window is open as fallows
In the above u can click the startup tab and disenable unnecessary Programs in the list (MSM Messenger and some ) and then click ok it will ask to restart the system. And then restart. after restart it will gives disenable information.
3. Clean the disks by clicking Start menuàProgram Filesà Accessoriesàsystem toolsàDisk Cleanup and clean all the Disks in u r system it will only cleans (Temporary internet files, Temporary Files, Downloaded programs and Some more) Shown on below.u can also cleanup from other software like Ccleaner (www.ccleaner.com Freeware).
4. And the last step to Defragmenter the disks in u r system b clicking Start menuàProgram Filesà Accessoriesàsystem toolsà Disk Defragmenter. It will defrayment the fragmented files and adjust the Disk space shown on below.
[Note: First analyze and after Defragment the every Disk and Every time