MSE replaces
Windows Live OneCare, a commercial subscription-based antivirus service and the free
Windows Defender, which only protected users from
adware and
spyware.
...
It includes the same anti-malware engine (dubbed "Microsoft Malware Protection Engine", or MSMPENG for short), and virus definitions that all other Microsoft desktop antimalware products share, including Forefront Client Security, Windows Live OneCare, and Windows Defender (Defender excludes the antivirus definitions which are separate from the antispyware definitions).
[16] http://en.wikipedia.org/wiki/Microsoft_Security_Essentials#cite_note-16 MSE will disable Windows Defender, as it provides protection against malware, not limited to spyware and adware.
[4]
