You probably need to run a registry clean up to stop a few things starting. That can be risky so I'd try a few other things first:
Remove enough files to leave 10-20% HDD free. Don't have any big files on the desktop. Run a disk clean-up and de-frag, instructions on Microsoft.com.
Install Avast anti virus and do a full check
Set-up two profiles, 'admin' and 'user' and set the 'user' as limited. Use that profile for everything except proper admin tasks.
After that hit Control/Alt/Delete and see what apps are running and what is using up memory. Use google to see what the biggies are and uninstall the trash.