How can I get full control of my computer? pls read details?

Still I'm the administrator of the system and have password.One of my friends played with some DOS Commands and now I can't open or reset my system secutity policy.When I try to open Local security policy or some thing from security options I get the Acrobat reader opened.What can I do with this?pls give me a solution either through DOS itself or any other way.I am using Windows security

Microsoft Windows 2000 professional

How can I get full control of my computer? pls read details?nortan antivirus

open the pc and take the battery out for about a minute place it back and close it up...now start the pc all memory of passwords have be reset and need to be set. It will prompt you to create a password and your good...good luck

How can I get full control of my computer? pls read details?nortonantivirus

Your file associations have become corrupted. You can use system restore to bring back an earlier version that hasn't been changed. If that fails then you can reinstall your operating system and keep your documents etc safe. Choose repair option. Good luck!
Does your windows 2000 have a restore? Go to start, then control panel, and then system. Restore should be top left on the screen.. Take the system back before the date your friend messed it up.. Earl
when u try to open the security options the reader opens up instead of resetting...hmmmm...
As Rowdy said, the file type associations in your comp are wrecked... but before you go for the drastic option of a Restore or even a Reinstall... try this go to folder options from the control panel, in that there's file types, click on that, click on the file type that's troubling you and then click on restore, may be it helps.
Some advice get rid of the stupid friend and reboot in safe mode and change it there.