Uninstall (not simply delete) all unused applications. These programs take up space on the hard drive and reduce the area for temporary files and load the Windows registry with dozens or even hundreds of file that need to be loaded at boot time. Both of these situations can drastically slow a computer down during boot and while running.
Perform some disk "housekeeping". Run Cleanup
to remove old temporary and orphaned files, cookies, etc. Read the directions carefully before using.
Run the Windows Disk Defragment Program. It is a tool for each hard drive. This program consolidates data and free space so that the disk has large, unbroken blocks of unused space to write temporary files - and makes reading data easier as it can be found in one place - instead of having to hunt all over the disk to find it.
Remove existing and prevent future "****" from collecting by using Ccleaner
aka "**** cleaner". When run and set up correctly, it will remove and prevent accumulation of junk files and spamware. Again, read directions carefully and allow updates to the program for maximum protection.
Lastly, install a good Anti-Virus program. Norton stuff is very good, BUT can slow a machine down considerably. Other choices are Avast
(free "Home" version available) or Viper
for about $30. Both are very good to excellent and have minimal impact on the computer speed.
Doing these few items should help a great deal - please rate this reply and good luck!