Do you mean Windows7 by Windows 2007 ?

First, you should check this issue in safe mode of Word. To start Word in safe mode [hold ctrl key while startup]. If typing in Word works well in safe mode, then this issue is caused by some add-ins. To fix this disable all add-ins.

If this issue also occur in safe mode, then damaged or missing fonts can cause the issue that word runs slowly when you edit in Word. To correct this problem, remove and reinstall the fonts.