As this system is a Pentium III then it is a fairly recent Compaq Presario so you will need to tap F10 when you see the red Compaq Logo

As for the system not performing the memory count, this can be corrected by going into the BIOS and under the 'System' heading you will need to change the 'System Post' from FAST to FULL. You will then need to press F10 to save and exit.