Unable to play games on my PC: Task manager is disabled

Hi,
I can't play any games on my computer. I went to my Task Manager and found about 48 processes running into my machine. I right clicked almost half of those 48 processes then hit the End Process tab.
Then I simply exit the window. When I restarted thinking that it needs a restart for the changes I made, I tried the games I want to play but it is still not working. I went to the Task Manager window again but I am having error upon opening;
Task Manager has been disabled by Your Administrator
And now I can't seem to open it anymore. I have run my anti virus scan to check if I was infected by any virus but there is no infected files found on my system. I never put any restrictions on my computer being the administrator of it. I was finding a solution on different sites, and found some answers.
But it has something to do with the registry that might be affected by virus. But before ending those processes, I don't remember doing anything except for trying to open my games. I want to know how I can rekindle this thing. I don't want to touch the registry because it may add a great damage if I go on a wrong procedure. I am using Windows XP.
Please send me some solutions.
