Problem starting Autocad 2002 as a windows2000 administrator

Hi
I wonder if any of you could help with a couple of problems I'm having
when starting AutoCAD 2002. When I log on as an administrator in
windows 2000, I get an error just when today starts to load. It says
something like: The instruction at '' referenced memory at
''.
The memory could not be read.
Click OK to terminate the program.
But when I log on as a power user it works fine, bar a message which
comes up with a registry error.
I don't really know what to do in these situations. I've tried
re-installing it. I've checked which processes each are running, both
exactly the same. I also checked the free memory virtual & physical,
both roughly the same.
Is there anything else I could try?
Thanks in advance
Rich