Well.. for ACDSee.. you can only do it for JPG's (and possibly RAW with the DCRAW plugin) but not for pngs, etc... and, there doesn't appear to be an easy way to convert your category entries into keywords which would be stored in the IPTC..

So, I would suggest at the least, you add all your category info into the keywords section using the batch set info utility... but even this will only be good for jpg's... I'll need to look into a 3rd party tool to help with this... this is why I like tools that write directly to the IPTC data for images (or use a sidecar file for things like NEF and PNG)... stay tuned.