Have you tried the following:
1) Install the game and wait until i 'frezes'.
2) Restart you PC
3) go to the Control Panel and start the 'Add/remove programs' tool.
4) See if you can find BG1 as one of the installed programs. If yes: Select it and remove it. If no: Hmm - this didn't work - reinstall your HD from scratch

5) Restart your PC
6) Install BG1 and cross fingers
[img]graemlins/greenbounce.gif[/img]
Insane