Yes, this can be done in order to reset all preferences and can be a way to fix any corruption that may be occurring in Reason.

To do this in Windows XP
First, quit Reason and then follow the following path;

C:\Documents and Settings\"Your User Folder"\Application Data\Propellerhead Software\ Reason and then delete the Reason Preferences.prf file.

Next, empty the Recycle Bin and then restart Reason.

The preference file will be rebuilt upon Reason's restart.