There are many reasons for this slowing but these are most important:
* Low Memory. Having enough memory can make the difference in speed. Eg., Windows XP runs very well with 2Gig or more, and well enough for most people with 1G, but a PC runs slow with less. Adding memory can be the least expensive and yet one of the most significant ways to speed up PC.
* Unused Programs. Programs you do not use or do not need, require space on your hard drives, and in memory - making computer run slow, and possibly startup slow. See your Task Manager for more details.
* Unused Files, Browser tracks, Folders, Registry Keys, etc. Download a program that will delete all these stuff. I'm with
mil shield http://www.milincorporated.com/milshield2.html from years and it detects and removes all you want in your computer, and not removes useful files.
* Disk Errors. Your PC spends much time reading and writing data to the hard drives. Slow computer performance can be caused by badly arranged or erroneous files on your hard disk. I use Error Doctor for these disk errors.
* Virus infection. These are small programs, using resources on YOUR computer, which you never asked for! Keep antivirus software up to date. I'm with
AVG http://www.avg.com/eu-en/homepage from years.
* Driver conflict. Some old drivers cause problems. Just download newer ones.