Thinkpads Forum

Hi I recently bought a Thinkpad 755CD. The laptop gets past the BIOS but won't boot from the hard disk. I get an "invalid system disk" error. I ran the BIOS self test and it passes the hard disk test. It passes all of the other BIOS tests except the video test although it seemed to be able to get through most of the video modes. I assume the hard disk is either corrupt or faulty.

I would like to try to install Win 95 but the problem is I do not have the floppy drive for it, only the CD-ROM so I have no boot device. Can I take the hard disk out and put it in another machine with a floppy, then install DOS and a CD ROM driver, put it back in the Thinkpad and use it to install Windows from the CD-ROM?

Or should I just try and find a floppy drive for it?

"invalid system disk"

Means it can't find the boot track. Disk could be erased or the boot track munged up. Or the disk caddy is not connecting completely.
Isn't the 755 an EIDE controller? You will need to take it out of the caddie to stage it in something else.

Thanks I put the hard disk in another old laptop and it was not even detected. Surprisingly I did manage to read from it using a USB to IDE converter on my main PC but it was unreliable and sounded like the head was crashing into the platter. I swapped the hard disk with one with Windows 95 pre-installed and it boots ok now.

I have a minor issue with it. Sometimes if I shut it down and try to power it on it makes two beeps and doesn't power back on. However if I remove the power cable and re-insert it it powers on fine.

subspace wrote:Thanks I put the hard disk in another old laptop and it was not even detected. Surprisingly I did manage to read from it using a USB to IDE converter on my main PC but it was unreliable and sounded like the head was crashing into the platter. I swapped the hard disk with one with Windows 95 pre-installed and it boots ok now.

I have a minor issue with it. Sometimes if I shut it down and try to power it on it makes two beeps and doesn't power back on. However if I remove the power cable and re-insert it it powers on fine.

Those are definitely interesting machines. I recently acquired one in excellent cosmetic condition, but it had massive corrosion from both a leaky standby and main battery, so I have to replace the system board, DSP board, and some other parts.

Have you checked the battery bay or standby battery for signs of corrosion? This can sometimes cause a problem as well.

What kind of hard drive are you using? I've been trying to upgrade my ThinkPads to SSDs (1 and 2GB PATA drives). I've found, and remember this trick from years past, that sometimes the drives won't detect unless you clip off the master/slave pins (no connection, and the drive is assumed to be the master drive). There also seems to be a difference between the connector for the caddy on the 760 and up, and the 755 and below (what, I don't know, unless some pins are tied to different lines than the other).

I've also figured out that the way drives report geometry can be a problem. For instance, the SSDs I'm using work properly with MS-DOS 6.22. Using a Compact Flash card or Microdrive with a CF adapter, I can only get a newer-ish OS like Windows 98 to work, presumably because of LBA addressing.