Space, the final frontier ....
The common wisdom on your Database Files is to NEVER shrink your data files. Space is cheap, but it's worth knowing how to shrink the size of your data files especially when you are running out...
How to Truncate Log files in Sql Server 2008
If your transaction log files are growing beyond their disk size, it's important to consider why your log file keeps growing?
Databases Log Files will use space to quickly write to disk the many operations it requires and thus some file growth is expected when you reach beyond the initial sizing of your database. When you notice continual growth of your transaction log file, you need to start looking at your backup strategy to help manage it. Did you set your recovery model to the appropriate one? Should you be performing more transaction log backups?
for more information on the shrinkfile operation, consider reviewing the tech doc at Microsoft. You can also read a little more on your database recovery model here to ensure you are using the right one for your set of circumstances!