computing power, you need maybe at least p 4 dual core cpu or maybe amd 32 bit system or 64 with maybe 2 GB ddr ram
something like that if you have a single core cpu and say your hfs server gets lots of users online it will ask to much resource from the single core and thus hfs can't operate faster when the hardware is not enough.

you can try to cluster maybe 3 or 2 high end computers to act as a single core, here more info
Citrix XenServer
Enterprise-class. Cloud-proven. Free
http://www.citrix.com/English/ps2/products/product.asp?contentID=683148i didnt try this yet, since i don't have another computer to test it with, the basic idea is simple
install the free version of XenServer to all the computers you want to use as servers and these computers will be clusterd together
then you only need to install the image file, iso like windows xp pro etc and run hfs through the whole cluster.

good luck