PureMessage for Microsoft Exchange: 'Error Code 1...' displayed during installation

Issue
An error similar to the following is displayed during installation of PureMessage for Microsoft Exchange:

Error Code 1 was returned when running 'c:\doc and sttz\admin\local settings\temp\1\bootstrap.exe' install exe 'c:\pmex_30\resources\sav\'

Sophos product and version
PureMessage for Microsoft Exchange 3.0.0

Operating system
Windows 2003 SBS SP2
Exchange 2003 SP2

What to do

The path displayed in the error message may vary according to the reason for the problem. The error may have one of several causes, including:

Check to see if another anti-virus product is installed.
If it is, go to Add/Remove programs and remove it.
See also the Knowledgebase article Installing more than one type of anti-virus software on the same computer.

Failure to uninstall an earlier version of Sophos Anti-Virus before installing the current product.

Go to Add/Remove programs and remove the earlier version Sophos Anti-Virus. However, you may receive a further error message
The feature you are using is on a network resource that is unavailable.
Refer to the Knowledgebase article 31519

Once you have completed the above, reinstall PureMessage.

If you need more information or guidance, then please contact technical support.