how to check if data carrier is inserted:

[MDell95]

i googled for quite a lot of time but i haven't found anything... i'm looking for a way to check if a data carrier is inserted: i have 4 free interfaces ( I:\ J:\ ...) which are not used, and always when i want open them with the application it tells me to insert a data carrier. how can i first check if there is a data carrier, without getting an error?