Performance of Windows Degrades After software installations/updates:
No spyware, malware nor viruses exist.

1.  prevent unecessary programs from running at statup
start >run >msconfig >selective startup >startup tab
Uncheck programs that need not run. Firewallls, antivirus,
intrusion dection and popup blockers may remain checked.

2. Install tuneup utilities and run the 1click maintenance
http://www.tune-up.com/products/tuneup-utilities/

3. Install and run ccleaner
http://www.ccleaner.com/

4. Install and run Ilsystem wiper
http://www.iisoftware.net/index.php?clean.html

5. Run scandisk
mycomputer >right click C: >properties >tools >check now
>automatically fix file system errors
If necessary, schedule scandisk on next reboot and reboot PC.

6. Run disk defragmenter in safe mode
start >shutdown >restart PC 
While restarting press and release F8 key continuously for boot menu.
Select safe mode.

start >mycomputer >right click C: >properties >tools >defragment now 
>defragment