Is there a BIOS or CMOS reset switch on the motherboard?
Otherwise the good'ol pulling out cell battery trick will do. You'll have to reconfigure everything in BIOS afterwards obviously.
In this case I'm more familiar with PowerEdge than ProLiant unfortunately.
Tell the HP support guys which sSPEC your new X5570s have so they check on their own. Being Q1G9 and SLBF3 for X5570.