Defragmenting Hard drives
The files when moved or created on your PC are stored into small fragments randomly on your disk drive. When you open those files it takes time to gather all those chunks and put them back together to form that single file. When you defragment your drive all those scattered fragments are arranged properly on the drive thus loading application bit faster. There is a Disk Defragmenter utility in windows,
Open My Computer > Right click on the disk drive you want to defragment > Select Properties > Under Tools tab click Defragment Now. But we recommend Power Defragmenter a small free utility by sysinternals which is faster and with various options



Delete Temporary, Junk and Obsolete files Clear cache
Clean all your drives for free space, we  recommend keep atleast 20% of your drive space free. Also, you have to clear the windows TEMP files, the web browsers temporary files, caches files, etc. All web browsers has that option. CCleaner will be a good choice for the same, it will analyze and clean all unwanted internet files, Windows Explorer files and system files.
Remove unnecessary Programs

Remove those programs which you don’t use anymore. This will free disk space and even help windows perform better. Also, remove the windows unwanted components like Indexing services & Outlook Express from the Add/Remove windows programs.

Keep PC updated
Look for regular updates, Enable Windows Updates, Updates includes major bugfixes which can be helpful. Look for new Service packs for better hardware compatibility. Update all device drivers, anti-virus programs and other applications. Hardware Manufactures keep updating their device drivers for better and smooth functioning. I have written earlier on a Free Software To Update Windows Device Drivers do read that.