I've had my Dell X200 for quite some time now, but haven't had the best of luck with this laptop.
Well, to start with, you need to install RedHat. I was lucky and my laptop came configured with two partitions. I kept the XP partition in place, deleted the D: partition, and created the partitions I needed for a RedHat install.
Booting the install CD was tricky, since at the time, RedHat 7.3 doesn't support firewire from the installer. Luckily, I had a pcmcia drive so I first booted from the firewire drive, and then moved the cd over to the pcmcia drive to boot from.
I remember I had all sorts of problems with the XFree86 that comes with RedHat 7.3, but eventually I upgraded to a version that worked with the new i830m chipset. If you install RedHat 8.0, you should be fine. I don't remember if I had any other issues during the install, but over the months, I've upgraded to RedHat 8.0 (upgrade in-place from 7.3, not a clean install), and manually upgraded my kernel to 2.4.20 with the latest firewire support, since I bought a firewire disk. The RedHat distributions technically support firewire, but most don't have very bug-free support.
Everything else installs ok:
It's a beautifully light and portable laptop, but I *always* suspend the laptop, and that has been a source of neverending headache. Two main power related issues:
A long time ago, I upgraded to RedHat 8.0. X worked out-of-the-box, but apm had the same issues. X still won't restart well (frequently). I added ACPI to the kernel, and that helped some, but in 2.4, there is NO suspend-to-ram support. suspend-to-disk purportedly works, but I haven't tried it. At least with acpi, I can detect the lid switch being closed, and when that happens, I put the machien into low power mode and kill -STOP various processes like mozilla and lpr which will keep the disk drive spinning. Since the machine is in low power mode, the battery lasts more than long enough to drive from home to work and vice versa. I still haven't upgraded to 2.6 which is supposed to support ACPI better.