ACPI:cannot locate RSDP

[xpod]

Upon installing unbunto in this pc i then attempted to do the same in an older pc and got the above message before it proceed to try and set up.It just eventually kept freezing

So discovering that "unbunto" was mabey needing more memory than the old pc had i then downloaded "xubunto"...Which again ,works great on this pc BUT still proceeds to display the "ACPI:cannot locate RSDP" message on other pc

I have googled it and there is some advice for changing boot options but im not to sure how i`d be going about that

Could anybody mabey spell it out for me if it`s possible

The pc in question is a compaq presario 5130 with 128mb ram and 6g drive

Strangely the pc has had xp pro installed on to it somehow(a friend who never knew any better)but dosent have a proper product key(maddness!)

So it`s formatted to ntfs if that has any bearing on the matter but ive tried and tried just getting the cd up and running ALL to no avail.

ANY IDEAS

edit:Sorry i forgot to mention that after displaying the message it then still try`s to install, freezing just prior to the desktop coming up.