sounds like a registry problem.

if you have windows xp cd.

restart pc press delete to enter bios
make 1st boot device CDROM
and Second boot device Hard disk
While still in bios stick windows xp cd in your pc and then say save and exit,

When prompted press a key to boot from Cd rom.

Proceed as if you were going to install windows xp
Carefully Reading what each screen tells you, (becarefull not to go to far)

Keep proceeding allong and you will be given choices,

When given the choice
Select repair windows xp

DO Not Use recovery console.

DO Not Use Automated System recovery


This will fix any windows registry entries you Really need, and Should allow you to Install shogun again.