Hi, 
It has been awhile since I tried booting the HP but...
bootserver = Linux 2.0.34
HP = 433
I had good luck with sun-rbootd with a 486-dx2-66 linux machine. Would boot 
with absolute reliability. (I mean like everytime....).  :-)
When I used the same disk, etc. but upgraded the CPU (& MB) to a K6-300 
sun-rbootd would hang and at the very least took a series of carriage returns 
(one after every packet) to boot at all. 
The sun-rbootp distribution from the ***.jp site compiled and ran first time 
off on the slower system.  
Doubt this will help but when desperate try the off-wall-ideas. 

Dave