My friend has a Computer which has WinServer 2003 R2 installed in it. When he try to install Win2000 on this machine, he is not able to.
When he boots the computer in WinServer 2003 ,he inserts the
Win2000 Bootable CD into the CD-ROM and and tries to run the
setup file . The Installation starts and at the bottom of the screen
it loads drivers and checks the hardware configuration.
After this the blue screen appears which gives an error messege
about ACPI(Advance Configuration Power Interface).
It says something like this "This system is not fully ACPI compliant,please contact your Vendor or visit a site(I exactly donot remember the website) to get information. You can disable the ACPI option in BIOS by pressing F7 key"
He was also not able to enter BIOS setup.

He has tried this Win2000 bootable CD on different Computers
but still they all face the same problem.
The same problem occurs when he uses WinXP bootable CD.

Does anyone have any idea why this problem is occuring?

He must enter BIOS and disable advanced power management.

The usual way is to press "del" key during boot-up. On some machines it is one if the "f" keys (f1-12)

If the BIOS is password-protected, then clearing the CMOS would reset the BIOS password. (either remove the CMOS battery for a minute or two, or flip the jumper for clearing the CMOS)

After the CMOS is cleared, all the settings would revert to defaults, that doesn't necessarily have to be correct.

I am not sure but there are significant differences in the way that win2003 (xp under the bonnet) and win2000 (winnt under the bonnet) use the frmatting on the hard disk. it is likely that you may have to update!