I have a Compaq Deskpro EN after changing hard drive from 8GB to 40GB get the message on start up error riser not detected will give option press F1 to boot and it does but can not reset defaults in BIOS and save and exit am stuck in this constant loop any help would be welcome.
I suspect that the BIOS in that system is not capable of supporting a 40 GB HDD. That is a very old system. Some of the older HDD have a jumper setting which lowers their capacity at a BIOS level. This may be a work around. Otherwise a BIOS upgrade may be in order or failing that it may be time to give up on the old girl.