In my previous post Fix STOP: 0x0000007B (OxF8968640, 0xC0000034, 0X00000000, 0x00000000), I described come remedies to that problem. The thing that started the whole thing was the following message.
I had Windows XP Home installed on my Dell Latitude E6500 laptop. I decided to upgrade it to Windows XP Professional. The upgrade completed without any problems. After laptop was rebooted, I had my nice login screen come up with all the user accounts listed. I clicked on my account and I got the above message. Since I have valid user license for Windows XP Professional, I clicked on "Yes" on the dialog box. Nothing happened. Usually a wizard starts that walks you through activation steps. I tried rebooting few times, booted in safe mode, repaired my installation. Nothing worked at all. I thought I could log into safe mode to do activation. Well, it told me that I can not activate copy of windows in safe mode. I tried to reboot with "Safe mode with Networking Support". That did not go very well because operating system refused to do so telling me that I have to activate copy of the windows before I could do so. After digging around and calling my preferential technical support at microsoft, I came to know the following things and fix for the problem.
So from above two issues you can see that I am in catch 22 situation and there was no way that activation wizard was going to come up. So here is the solution to the problem.