This is an irritating issue, It usually happens after a repair install windows wants to be activated to log on. When you click on activation it disappears, only your background and pointer remains.
The problem is caused by windows reverting internet explorer back to version 6. Your windows activator needs IE to work. So what we need to to is update IE to version 7 or 8 then simply activate.
Another problem tho, sometimes you need to get into windows normal mode to update IE6, to activate (Typical Microsoft). Issue with an issue and a cherry on top.
To solve this problem we need to boot into SAFE MODE Restart computer, while booting before windows load press F8 a couple of times until menu appears and choose safe mode.
in safe mode we click on start then run or (start button + R on keyboard). In Run dialog box you must type the following exactly case sensitive "rundll32.exe syssetup,SetupOobeBnk". Wait a moment and restart into normal mode, windows XP 30 day trial has been reset.
I went and made a *.bat file with the code to run. I had a need for it a couple of times before.
If you were wondering or in need of windows 7 30 day trial reset it is "slmgr -rearm" but can only be used three times in a row.
Remember: This is just a way to get into windows to repair and activate your windows copy with legal license.