"Device Driver for the Standard 101/102-Key or Microsoft Natural PS/2 Keyboard" Error Message When You Try to Enter Standby
This issue may occur if Adobe Type Manager is installed on your computer. Certain versions of Adobe Type Manager (version 4.0, for example) may not be compatible with the power management features of Windows XP.
The updates from Adobe might help.
If that does not help, see this article for other cause for the problem and the solution: ( Originally written for Windows 2000 )