Can a older version be installed after a latest trial version

I am using photoshop CS- 5 trial for 1 month. After the trial period is over can I install the legal copy of photoshop CS-4 which is a previous version than the trial version. Does the system accept the same.

I know that trial photoshop 4 can not be installed after trial photoshop 5 as the new trial should be the latest. But my query is about installing the Legal Older Version after the Latest trial version.