Desktop properties window not opening

Use tweak #128 in the righthand column) of this link to fix your tab.
http://www.kellys-korner-xp.com/xp_tweaks.htm

This missing tab is a pretty sure sign that you have or had a malware infection. You should perform a scan of your computer using these steps:

Restart your computer in 'Safe Mode with Networking Support'.
(To do this: Power on your computer and start tapping the F8 key at the top of your keyboard rapidly until the Windows Start Menu appears. Then select the Safe Mode with Networking Support menu option and press the Enter key)

Open your web browser and go to www.malwarebytes.org

Download their free malwarebytes program from their main page

Install the program on your computer and run it.

Update the Malwarebytes program and do a full scan.
(You may be asked to restart. Do so, but use F8 key to return to Safe Mode)

Let us know the results of the scan and whether or not any symptoms persist and we will troubleshoot deeper.

Cheers!