Any laptop of the right thinkness and ATA speed should be fine.
There shouldn't be any real reason to look for HP specific drives as it
seems it takes a fairly standard 9.5mm drive. Faster spindle
speeds will help performance, but at the expense of battery draw and
heat. If it's one of those hot P4 monsters, I'd be a tad wary of
using a faster/hotter drive than spec. Otherwise, if it's a
Pentium M, then the heat output should be less worrysome.
I believe there are 3 sizes of laptop hard drives, the main difference
is their thickness, and the amount of power they draw. Search
pricewatch.com. I saw a 80G 4200RPM, toshiba drive, 2.5"x9.5mm, for
$112, from memorylabs.com...under details "for ..... hewlett packard"
Matt