Have you tried resetting the bios to default values. Do this by entering bios. Thinkpads do not react well the removal of the CMOS battery. From experience if you do that the system will become useless and the only fix is to return it to the factory to have the Motherboard repaired as they call it (they reprogram the bios). After resetting Bios to defaults set your HDD to auto then your boot order to CD, Floppy(if equiped), HDD. THen see if you can install the OS on the Internal hdd. This is the route I had to take on my ThinkPad G40.