I know this is an OLD thread, but I thought I'd share my M505X story in case it'll help anyone out there still running this nice laptop.
I've had my M505X since 2004. Here's what I've upgraded:
-maxed out the RAM at 2GB @ 166Mhz DDR (PC2700)
-running the WD scorpio 250GB drive (they eventually came out with a 320GB version, but at this point, it's not worth it to me to upgrade to "max" out the HD)
-upgraded the internal wifi minipci to an Atheros that by chance supports...