I'm trying to resize my root partition down from aour 30 gb to around 10 gb: I'm dual-booting Redhat 9 and Windows 2000 pro owith a 40 gb HDD. I currently have 8 gb set for windows and around 30 gb for Linux, but as the root partition is ext3 Windows is unable to access it. Therefore I want to set up a 20 gb shared partition on which I would store any data (text files, movies, music, etc.) that would be used with both OSes. Can I do this without formatting my root partition?
I also have another question. My fiend is currently dual-booting Redhat 9 and Windows XP Pro. He recently got a new 160 gb HDD and plans to also boot with Slackware 10 AND Mepis. When I set up my dual-booting I only set 1 gb as Swap, but with all these extra OSes should he have more?

Resizing tool: parted (text mode), qparted (graphical). parted is probably easier to get (should be on your installation cd), but may be harder to use, especially for the first time. Read help and be careful. If in doubt, ask.
1GB swap is usually too much (maybe if you're rendering films or so..). 512MB is all what's needed. Also, you don't use two systems at the same time if you dual-boot, so one swap (and max 512 MB) is enough. All Linux distros can share the same swap. Also no data that's needed after a reboot is kept on swap. More distros doesn't mean more swap needed. I hope I'm clear...

The easiest way to non destructively manipulate your partitions is with bootit ng (www.terabyteunlimited.com). Get it and make a boot disk and boot from it. Make sure you press cancel or escape at the initial screen so that you can go to the partition work dialog. The rest should be very intuitive. The only caveat is that I don't think you can change the order of your partitions without deleting them and then recreating them.

Beware, Windows XP doesn't like shrunken or moved partitions. When I slid my Windows boot partition to the front of the hard disk and shrunk it, it hung before the login screen. It seems that you need to clear the boot signatures in the MBR (bootit let's you do this) and delete the keys in HKEY_LOCAL_MACHINE/system/mounteddevices (something like that) before you boot from a shrunken/ moved Windows partition. Other symptoms include hanging when uninstalling applications.

1GB for swap is already more than enough and anything more would be an overkill in most cases. The swap behavior in Linux is different than in Windows, which generally uses swap more to free memory for other applications, so the Linux equivalent for a 1gb windows swap file is less.

Thanks a lot. Actually, I DO edit/rip/compile to Divx movies fairly often, so I think I'll leave my Swap at its current size (It can't hurt, can it?). I'll try out qparted and bootit ng, see which one works best for me. I used fips to orignally partition my windows vfat hdd, but of course that only works on fat.