No need to reinstall CS1 prior to installing the CS4 upgrade.
Just install CS4, enter your CS4 upgrade serial number then enter your CS1 serial number when prompted.
Note: the actvation server for CS2 and earlier was shut down by Adobe last year so, to install CS1, you must now download a new non-activation version of CS2 and use the new serial number provided by Adobe.
Operator error! All good now