Can't boot on HP Vectra with install CD or floppy

I'm trying to install 8.1 on a slimline HP Vectra but it won't recognise the boot on either of the first two CD's nor will it boot from a boot floppy made according to the instructions in the book (using rawrite). With the floppy, it simply comes up with boot failed. I've tried it with a RH rescue disk and it boots off that OK (until it tries to find the OS on the hard disk of course). Any ideas what could be going on here? It seems to find the CD OK (atleast in the bios etc) but just won't see the boot sector for some strange reason. Thanks. Peter Nunn.