Error: The image in the archive which would be used to upgrade
Error: system number 1 does not support the same feature set.
Cisco it seems included this sanity check,as of 12.2(35), to prevent you from accidentally changing the feature set during a IOS upgrade, not a nice thing to happen on a production switch, when things go belly up.
You will get the above error when upgrading the IOS and changing the feature set. IE if you upgrade the image from IPBASE 12.2(35)SE5 to ADVIPSERVICESK9 12.2(25)SEE4.
So to bypass this, you can add the /allow-feature-upgrade parameter, to the archive download-sw command.
#archive download-sw /overwrite /allow-feature-upgrade tftp:10.1.1.1/c3560-advipservicesk9-tar.122-25.SEE4.tar
If you need more info on how to upgrade the IOS on a Cisco 3560, visit Cisco.