Problem installing .NET Framework 4.0+ on Win7 64-bit.

Hello good people of WindowsSeven Forums!! I have a little problem which I would like to some assistance.
Some time ago when my PC was running on Windows 7 Ultimate(32-bit), I installed .NET Framework 4.5 as part of Visual Studio 2012, everything went on just fine and I used Visual Studio without any problems. However, after my bro installed a 64-bit version of the same Windows 7 Ultimate edition, I cannot seem to install any release of .NET Framework(specifically 4.0 and later). I get an error message with an error code 0x00000BC9, requested operation failed, with title Installation did not succeed.
Doing some research on the error code I found out it could be due to an update error. I tried checking for updates and all I get from Windows update is 'Restart your computer to install important updates'. Hitting the 'Restart Now' button and trying after reboot only brings me to the same screen again.

What I have tried.
Both MS FixIT and .NET CleanUp Utility but they were of no use.
MS Windows Update Troubleshooter. Fixed some errors but problem still persists.

What do I do now? Please help me as many applications I use depend on .NET Framework, especially Visual Studio.
Thanks in advance!!!
Edit
Here's a link to the generated log file. Microsoft services