Try downloading and running the delta patch for MSRT from the the Update Catalog.
https://www.catalog.update.microsoft.com/Search.aspx?q=KB890830
Select the x64 for Windows 7 (second on list) Download and you will be presented with two files (select bottom file).
Patch file (~6.77 MB): windows-kb890830- x64v5.77delta_acd7b02e03c86f374a14271a7b0844a3e4ad64dc.exe
Note: See EDIT at bottom of this post.
Save file then double click to install. It should update the version of mrt.exe on your machine to 5.77.16547.2. If successful the Malicious Software removal Tool should appear. Do the default Quick Scan then reboot computer and check Windows Updates again.
Hope this helps*.*
~bhringer
EDIT*: For ease of access, below are direct download links for the appropriate 32 and 64-bit versions,*
32-bitwindows-kb890830-v5.77-delta_a9f4bcd60fdf765b24ed4b3c30af93a31d3517d4.exe
64-bit
windows-kb890830-x64-v5.77-delta_acd7b02e03c86f374a14271a7b0844a3e4ad64dc.exe
How do I now If I have 32 or 64 bit?
Select the Start button, right-click Computer, and then select Properties.
Under System, see the system type.
https://support.microsoft.com/en-us/help/15056/windows-32-64-bit-faq