Windows XP - Fix various woes

Q1. How to fix Windows while happen some urgent error?
I ever happen an urgent error in my NB (Microsoft Windows XP). The message was as bellow

STOP: c000015 Hard Error
Hard Error

Finally I fix this problem use the following procedures.
1. Reboot the NB and use M.S. Windows XP CD to boot the system.
2. Important: Don't select the Repair the Windows at the beginning. Select the "Setup Windows" first.
3. Press F8 to allow the Windows License
4. Select the "Repair Windows"

Q2. Add Environment Variable Path into Windows XP system. The procedure can refer the following diagram