First thing's first, since you can still boot both, if you have a floppy drive, make boot disks for windows and linux just to be safe. For windows make boot disk and ERD.
Windows boot disk
In slack, the command I believe is makebootdisk
slack boot disk
Also, if you can burn, now would be a good time to backup anything you can't afford to lose.
With that stuff out of the way, the first thing I would do is go back into slack and rerun liloconfig, making double and triple sure that the answers you give are correct, also paying attention to make sure you tell it to write the MBR on the drive you plan on booting to from the BIOS every time. (Which one, either /dev/sda or /dev/hdc is up to you. I assume you know the tendencies of your own board.) Then of course run lilo to install it.
If that still doesn't get it, then please su into root and post the output of the following 3 commands:
and we'll try and help you from there.
Also you say your windows C: is on /dev/sda1, but your lilo.conf says it is /dev/hdc5:
# Windows bootable partition config begins
other = /dev/hdc5
table = /dev/hdc
# Windows bootable partition config ends
If you are correct and your lilo.conf is wrong, you need to make sure and correct it the next time you run liloconfig.
Btw, in case you don't know, when we talk about the "/dev" stuff:
- /dev/sda is the drive on SATA 0
- /dev/sda1, /dev/sda2, are the 1st, 2nd partitions on SATA 0, and so on
- /dev/hdc is the drive on IDE Secondary Master
- Same numbering as above (/dev/hdc1: IDE 2nd Master, Partition 1, you get the idea