I'd give an 80% chance of that HDD completely dying in the next two months. Somethings wrong with one of the heads most likely. I'd guess the ps2 is less picky about read errors and whatnot, but I do know a clicking HDD that randomly doens't show its contents is living on borrowed time.
I'd suggest wrapping it in an antistatic bag, seal the bag up completely, then putting it in the freezer for a few hours. QUICKLY get into windows (if you need to xfer files), and toss it in the trash, or on ebay for a few bucks as parts only.
As for the mem stick - sometimes I deal with rediculously slow WinXP installs that show the icon, but don't show the thumb drive for 5-10 minutes, if at all (reboots often needed).
v7 & Messiah2
location: Iraq; coordinates: classified; mission: replacement for 'shelled' ps2
v10 & Matrix Infinity
location: my room; mission: Army reserve...