if you do a new install does it still happen?
where exactly is this "click" sound coming from?
perhaps it might have something to do with the frame buffer or the k6-2 cpu... the mandy 9.1 errata page has a few notes on issues with amd k6-2s...
http://www.mandrakelinux.com/en/errata.php3
if the pc is working "fine" with windoze then the hardware is probably not to blame...
a couple things to try would be to remove the ati video card and activate the onboard sis video chip to see if it works (mandy should see that you removed the ati and walk you through setting-up the sis)... if it does, then you've sorta isolated the issue to the ati card... but since you've tried it on another os, it's probably a configuration issue...
the video configuration (x server) in mandrake linux 9.1 is in the file:
/etc/X11/XF86Config-4
you could edit it with vi or use something like the xf86config command at a command prompt... of course if you can't get even a prompt you'd have to access the disk through a floppy or cd-rom based distro... the mandrake cds have a "rescue" mode for this sorta thing... hit f1 (i think) at the cd boot splash and then put "rescue" without the quotes at the prompt... then all you have to do is mount the hard disk and edit the x configuration file...
it might also be helpful to try booting a live linux distro such as slackware-live or knoppix to see how they work with your ati card... if they work well, then (in theory) you just have to configure your XF86Config-4 in a similar manner... (mostly save, copy, and paste stuff)...
http://www.slackware-live.org/
http://www.knopper.net/knoppix/
of course, it's also possible that your problem has nothing to do with your video card... mandrake is considered by many as the best at auto-detecting and setting up hardware such as video cards and such...
keep posting... good luck.