I am also facing this problem. Created some dummy records in different modules and when I tried to delete them, there's always something that I could not delete

I have the same question - and will explain why. ;-) I toyed around a bit to get to know OpenERP, filling in data that don't really make sense or customers with silly names (just to check what's happening). Now I want to clear all (dummy) data and start anew, this time with "real" (or at least plausible) data to show to my customers. The internal references between datasets and the workflow restrictions make it very hard to delete them (i.e. customers or orders) as whole lists, so a general "kill them all" over all datasets would be helpful...