Can't find missing features in SharePoint 2007 preupgradecheck

After running the PreUpgradeCheck I have the following missing features.
Information Only : Feature Information  
The following features are either installed or referenced by the content
Name = [Unknown], Feature id = [44a616cd-0d3d-4747-a2a6-0260499ba06f], Reference count = [9], Scope = [Web], Status = [Missing]
Name = [Unknown], Feature id = [39366b48-d596-4010-9957-6da549d5de69], Reference count = [9], Scope = [Web], Status = [Missing]
Name = [Unknown], Feature id = [577e5b61-7893-4b76-9950-9e8be7282478], Reference count = [9], Scope = [Web], Status = [Missing]
Name = [Unknown], Feature id = [1b8e70bb-534f-4934-8f3f-d432470022b3], Reference count = [1], Scope = [Web], Status = [Missing]

I have searched on Google and can't find any references to the Id's.
How can I find out if these features are webparts, sites or custom features.
Any ideas what I can do now?

ERMA_ITAsked:
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KoenVostersConnect With a Mentor Commented:
As they have status missing the are not working.

You can forcefully remove them with featureadmin:
http://featureadmin.codeplex.com/

stsadm -o uninstallfeature -id [GUID] -force
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