Does it boot into safe mode? If it does go to Control Panel > System > Advanced > Startup and Recovery > Settings > uncheck 'Automatic Restart'. This stops XP rebooting when it BSoDs, allowing you to note down the "stop error".
Unless the hard drive has died, you should be able to view the data from another install of Windows by using a caddy. If the data is corrupt, the recovery software on Hiren's boot CD should be able to get them back - don't recover to the drive you are recovering from.
XP can be installed from USB stick.