The non-solution: I got into my system with a boot disk, ran LILO which returned with "Added Linux *" then it still didn't react to any Shift, Alt or Ctrl key. While I was in my system I read the LILO doc which talked about installing LILO, then activating the Linux partition, then rebooting. Problem there was that after I activated /dev/hda3 (Linux), /dev/hda1 (Win95) was not bootable anymore. With cfdisk you can create two bootable partitions, but that also didn't work.
The solution: Brad was right that with a Debian installation disk you can mount an existing root and swap partition and make it bootable (again) without touching the rest of the system. Just read the menu items carefully and pick what you need. I had it done and fixed in 30 seconds!!!! Kudos for Brad and Debian. But while I'm at it: I would like for LILO to come up at boot without having to wait for the beep and a slam on either Shift, Alt or Ctrl. There was something in the LILO doc, but has anyone experience with such a setup and what do you have to watch out for? -- Hans P.S. For the curious: After I moved my PC to my new location it started rebooting in the middle of whatever I was doing, especially in Windows, but not at regular intervals. I took the machine apart and indeed there was a DIMM which was not quite correctly mounted in its socket and that was probably due to the move. But after I fixed that it still did reboot at random. (I checked power cables, power levels from the mains, etc. too, but this also didn't help). It didn't seem like a Windows problem, but I reinstalled it anyway and during the install it did it again. I took the PC (P200MMX, 64 MB RAM) apart again and found that the CD-R was quite hot. The CD-ROM was quite hot too and when I touched my HD (Quantum 3.2G, 76 k RAM, 1.5 years old, in use 10-16 hours a day during that period) I alsmost burnt my fingers. I kept the case off, put an ordinary house fan on the open side and for already six hours no problems whatsoever. I have to note here that I moved from a house with A/C to one without and that temperatures here in Taiwan are in the 90-95F range during daytime in summer. This Quantum HD makes a lot of noise too and I already have a replacement IBM 6.5G, 500k RAM ready. Awesome disks, these IBMs and very quiet too. After recapping further I think that when Windows was using the Quantum disk a lot for swapping the rebooting occured. Linux doesn't demand so much from the disk, so that's why this random rebooting only occured once when I was running Linux.