Determined there were 7GB of logfiles in :
C:\program files\common files\microsoft shared\web server extensions\14\
Trying to delete/move failed - access denied because files are locked
Found this excellent article by Doug Allen:
http://blogs.c5insight.com/Home/tabid/40/entryid/401/SharePoint-Usage-Logs-Not-Being-Removed-Fixed.aspx
Quick Fix:
On SharePoint Server server - restart SharePoint Timer Service (services.msc)
Log into SharePoint Central Administration
Go To 'Monitoring'
Go to Timer Jobs - Check Job Status
Find Microsoft SharePoint Foundation Usage Data Import and click on it.
Click 'Run Now'
This should blow out the log files fairly quickly.
