Can't install codecs

I’m trying tio install nimo codec pack and My system will not allow it to install.
I always get an error message saying that error opening file for writing.
It’s becoming a pain in the butt as I am unable to watch some of my movies.
help
G O

What OS are you running?

Is there a file specified that cannot be opened?
If so, please fill us in on what the name of the file is.

If you are running Windows 2000 or XP, are you logged in with a user that has administrator rights?

I’m running Xp Pro with duron 850 and 512mb ram.
I have admin rights.
I have tried to install several different packs.
Nimo and a few others.
It always seems to be the codecs that won’t install, all the programs will.

well if it keeps up I’ll just install Win 2000 Pro and running my files from there.