sure if you plan on using both install the dictionaries in compliance to mstardict instead of qstardict because mstardict expects the dictionaries to be stored in myDOCs/mstardict. If you will only install/use qstardict then you could folder up the dictionaries where ever you want.

If you dont have dictionaries FIRST THING is to search google for babylon stardict torrent that would include a large package of dictionaries that are likely to appeal to you. Im not sure if they are compressed or not but i will assume they are so you have to use 7zip or something and it will reduce them to like 4 seperate files per dictionary.

You got your dictionaries, now hook the n900 to your desktop in mass storage mode create a folder called "mstardict" and then copy and paste all the dictionaries. Once transfer completes detach the N900 open mstardict check settings to make sure dictionaries are checked for use and let it index the dictionaries done. For Qstardict read my post on this page to get the same results for mstardict.