100% Of CPU Consumption

I recently installed Windows XP. When editing a Microsoft Word document, the system was freezed and no respond. I was forced to suspend the editing. I tried to terminate the MS Word, but have to wait 2 -3 minutes because the CPU is 100% occupied.
My computer is P-III with 733 Mhz and equiped with 320MB RAM. The size of file I edited is 1.62MB.

Could any one can gives me help and your help would be appreciated.

Kenneth