After a process of elimination, I found that the Service "Dell Data Vault" appears to be the culprit. Try disabling this service in MSConfig.exe and reboot. This stops the buzzing/freezing for me. Further, if I re-start the service (type Services in the Start menu...), it immediately causes buzzing, and then this occurs every minute or so.
I imagine that uninstalling the Dell DataSafe application will uninstall the Dell Data Vault service, but I haven't tried that yet.
I hope Dell are working on this.