"Minimum processor speed: Pentium II 233 MHz"
http://h20015.www2.hp.com/content/common/manuals/c00043892/c00043892.pdf

Sadly, you may be just under the mark of where the software will consider the host machine to be acceptable. Try another computer.

"Is there somewhere in windows where I can tell the os to ignore this message, & install it anyway?"

Most likely not. This is a closed source OS and the same goes for HP's drivers. Unless they (HP) offer you a fix, then you have the wrong printer or PC.

Bob