SQL Server 2008 log directory has too much dump file
Start checking the log - the dump files are that - dump files. Logs should indicate why the server crashs so often. Check hardware issues. Are you properly patched up? Do that - install the last CU from SQL Server Release Services.

If nothing helps, then a MS PSS ticket needs to be opened, they can analyze the dump files. This likely leads to some hotfix, in which case it is a free ticket.

But first check logs and patch up the server.