This may be an issue with the music that plays during the installation of the game. Try turning down your sound card hardware acceleration level to 'none', then try the install again.
To do this:
1. Click Start, then Run.
2. Type: dxdiag and click OK.
3. Click on the 'sound' tab.
4. Move the sound hardware slider down to 'none', then close DXDiag and try installing IL-2 Sturmovik: Forgotten Battles again.
To do this:
1. Click Start, then Run.
2. Type: dxdiag and click OK.
3. Click on the 'sound' tab.
4. Move the sound hardware slider down to 'none', then close DXDiag and try installing IL-2 Sturmovik: Forgotten Battles again.