I have just installed a sata dvd rw, mobo is an ASUS A8V series and the os is xp home, unfortunately the system does not "see" the drive..............any help gratefully received

Can u see the drive from BIOS? Did you overclocked ure frequencies? Most likely u missed some setting in bios regarding sata devices. Look in bios, u may have some answers there

the bios sees the 2 hdd.s and both dvd's installed previously (all ata) but not the sata....no overclocking undertaken

Sata devices ar known to suck up a lot of power, try starting the pc using only one optical drive connected(SATA). Check BIOS to see if your SATA controlers are enabled.

the electrical load should be OK, I have a total demand well below the 450w psu, I will try however. The sata controller is enabled......begging to doubt the drive!!

I'm begging to doubt the drive myself. Try installing the drive on another pc. See if it works