You could also look at your file growth settings? is the default at 10% still? think how bad that is when you start reaching big sizes?

Maybe set the rate of growth to a fixed amount, like 100MB or 500MB etc., instead of the default 10%.

Look for a report called EM Task Pad, this will show you how much of that data file you are actually using.

Maybe look at resizing the file and then reorganizing your indexes etc.

Inevitably, you will need to either increase the existing disk, or extend the data file onto separate disks.