I searched 'new hard drive keep old system' here at LQ and turned up 11 pages - read 18 of the threads that seemed most relevant but despite that, I didn't see anything that fit. I know there's at least one thread that's close to my situation, but I didn't see that one. Also read the 'Hard Disk Upgrade Mini How-To' and regrettably got sucked into the 'Multi-Disk How-To', and those didn't seem to address some questions I have. So here goes:
hda1 is W2K, the extended partition is Debian, and hdb is Slack. hdc/sr0 is a dvd-rom and hdd/sr1 is a cd-rw.

I just bought an 80GB drive (on sale and with two rebates!) but I can't do a /dev/hde. And, as I understand it, I'd be bringing my new drive down by using it with one of the old ones. The new one's 7200 rpm, etc. and the old ones are 5400 (or less) iirc. But is this just if they're on the same channel? Should I do an [hda (80GB), hdb (cd-rw)], [hdc (20GB), hdd (dvd)] or something like? Or would that be worse? Should I just forget the second drive and use the one new hard drive? The new one is plenty of space but I like having dual-drives.

So there's the main issue of ultimate arrangement of the four drives. Then there's also what do with the three operating systems. I don't care about the W2K, or even the Debian, but I'd as soon keep them as not if only for the trouble I went through installing and configuring and their usefulness for troubleshooting. I also don't have an extreme objection to reinstalling Slack but I'd rather not, for the same reason of mostly wasting effort. But I'm kind of confused about the possibilities. It was easy to add the second drive and install Slack but swapping a drive seems more complicated. I could just stick the 80 gig in as hdb and reinstall Slack but I don't think that's the way to do it. And I could put it in as hda and copy Slack over with some revisions but that's probably not idea, either, and with LILO being on hda, that seems to be another difficulty. I think I need to rearrange the whole thing, but I'm not sure how.

Y'all are a lot of help.

I'm too stupid to run Windows, much less Linux, much less Slack. I did some more reading a few hours ago and was all set to go '80GB/DVD+20GB/CDRW' when I realized my cables were too short (or my case too big) and didn't feel like getting new cables, so I just did '80GB/20GB+DVD/CDRW' - just shifted hda to hdb and stuck the new one in. I think I'm going to stick the 15GB in my Celeron. I also didn't feel like backing up *everything* so I installed Slack to hda and was going to copy some stuff back over after that, but I fscked up my backups. So there I am, running with the case open with one unhooked hdb and a temporarily jacked in 15GB drive, busily 'cp -aR'ing stuff over. Hoping I don't short circuit crap with a (physically) unmounted hard drive humming along. I seem to have missed some stuff, too. Maybe some symlinks - I had to change a bunch, because /home was a symlink to /usr/local/home and now it's a regular /home again. So stuff like xmms seem confused. mpg321 (and hopefully ogg123) are okay, though. Ah well. The drives are recognized, Slack's installed, I'm on the net with mozilla and all my bookmarks and mail and all my crap and I'm able to post this. Guess I can't complain. Oh, and I edited Slack's lilo.conf and Debian's fstab and Debian booted and I played a game of pinball in W2K , which happily boots from hdb. Didn't spend enough time in Debian to see if everything was good, but it seemed fine.

*Now* will someone tell me how should have done this *intelligently*?

Oh - bonus about the fresh install - no KDE or Gnome on Slack. Just fluxbox and twm. I went ahead and installed it last time but forgot which was what so didn't want to uninstall them for fear of taking out key libraries - this time, I just said 'gimme the libs, hold the desktop'.

Second 'oh' - I'm getting in the ballpark of

Sometimes higher, sometimes lower. I searched for stats but didn't see anything specific. Does this sound reasonable, great, sucks? Things seem pretty nimble, but I dunno.