You can pretty easily delete it, see here: http://technet.microsoft.com/en-us/library/cc788042
It tracks changes in ntfs volumes in some older OSs like 2000 and 2003, but it only track changes. It can be deleted, but as MS points out the worst that could happen is you may need a complete volume scan.
Thanks for your quick and helpful reply!
A final question:
Is it normal that the journal is so big, and what would be your recommendation? Should I leave it as is or delete it?