I can't fix my Dell Precision M50

[danielsender]

My Dell Precision M50 has 2MB of ram and two disks. In the main slot I had windows XP and in the secondary bay I had Ubuntu 16.04. The grub loader was in the secondary disk and the booting sequence in the BIOS was set to go first to the secondary disk. Everything was fine until the XP disk started giving me input/output errors so I concluded that it was time to put a new disk and re-install a win system. Since I had a legal win7 installation disk, I used that and apparently the installation went OK, but after a couple of reboots the system would not reboot and the repair operation wasn't successful. So re-installed one more time and at a different number of booting/rebooting sequences the problem came back. I tried with another brand new disk with the same results. I ended up trying at least 7 times with different bad results. But the most surprising thing is that Ubuntu wouldn't boot from the second disk, with the system saying that it couldn't find a bootable disk (or something like that). Finally I was able to install win7 in the first disk, but randomly sometimes it wouldn't boot.

I ran a Dell hardware diagnostic CD and everything came out 100% fine. Suspecting that it could be related to the BIOS, I resetted the BIOS (alt-F), later disconnected the RTC battery and the situation wouldn't change. I tried re-installing the BIOS (A12) on the working win7 disk and it refused saying that are the same versions. Running with the /forceit and /forcetype wouldn't make any difference. Reading in some forums that there is a A13 BIOS version I looked for it and found that it was only available in some service CD that comes with some battery (??).

I would appreciate any suggestion.

Many thanks in advance.

Daniel