Why are the Task Manager, Registry Editor (regedit), and Command Prompt (CMD) disabled?
There are two main reasons that these are disabled: malware and corporate policy. This page is only meant to help with the former, as bypassing the policy of your company is not legal and is violating that agreement. Malware often disables these three common tools to prevent you from using these presumably for removing the malware.
How do I enable them?
First, you will want to remove the malware that caused this. Scan your computer with whatever antimalware software that you have and maybe with a few of the free online scans (listed on the Helpful Links page). If that doesn't remove it properly, you may want to consider joining an online forum (some also listed on the Helpful Links page), reading their instructions, and posting a HijackThis log.
One the malware is removed, Kellys Korner XP has a very useful VisualBasic Script (VBS) that should enable all three of these for you here