IL2FB was giving me lots of problems. Freezing, reboots etc so I uninstalled it using Cleansweep. However I had to delete the cleansweep backup becasue of low disk space. When I tried to reinstall IL2FB I got the message 'Error applying transforms. Verify that the specified transforms paths are valid D:1033.mst'.
This can also occur if you delete without using the IL2FB uninstall option in the Add/Remove programs in the control panel.
I have XP. It appears you must remove all register information relating to IL2FB install and transforms Where you find this in the register may vary. Backup the register. Go to regedit.(start run type "regedit"). I found the installer entries in HKEY_LOCAL_MACHINE/Software/Microsoft/windows/correctversion/installer/userdata/produccts/ad217fd85......./install properties.I then deleted these entries and I was able to install the game.
If you cannot find this entry just do a search on the following IL2FB or IL2-STURMOVIK FORGOTTEN BATTLES in the register and delete all entries you find.If this does not work keep deleting all entries to IL2FB that you find. You can ignore the hundreds of keys to locations like missions, wav files etc.
8df712da-d3254fd0-8de8-e2d78fcdc3 ad217df8523dodf was my product code in the reister you can search for this code.. I dont no if this is the same for all discs.
Hope this helps anyone with the same problem.