Dbl Click on .msi – access to specified device, path, or file is denied

I am unable to run any .msi files

– I have tried to reinstall the microsoft Installer
– I have followed an MS remove and reinstall process that renames the old and then reinstalls the Installer Redis 3.0

I still however am unable to run any .msi files. Running Win2000 SP4

Appreciate any help / suggestion. Thanks