Regarding the hogging of the CPU:
When watching 1080p videos or listening to 320KBps MP3s, my old 2.6GHz Dual Core (4GByte RAM) clunker starts to act up. For no apparent reason I see with Process Explorer that all available computing resources are fully used up and video/audio starts to stutter. After I terminate Foobar2000 or PotPlayer, about 60% (on average) of available resources are still being used, but now by the Windows Management Instrumentation service.
A little bit of Google research revealed that this service and the services that depend on the WMI service are actually started in the wrong order. So I created a little batch script that stops the WMI service (and dependent services and restarts these services. Sometimes I must execute it more than once, but afterwards I don't experience any stutter anymore.
So if your system is suddenly consuming a lot of computing resources, you could apply this trick instead. Although it sounds a bit silly, it works like a charm on my system and it might work on your system too.
NET STOP iphlpsvc
NET STOP UALSVC
NET STOP Winmgmt
NET START Winmgmt
NET START UALSVC
NET START iphlpsvc
Those are the names of the services that need to restart in Windows 2012. While I don't think these service names are different in Windows 7, I wouldn't be surprised if they are.
Regarding the installation location:
Whether you install software on or off the C:\ partition, as long as Windows is able to access that location, Windows as a whole and that piece of software remains working just fine.
For years my systems contain at least 4 different partitions, the 1st is only for Windows itself, the 2nd is for the programs I install, the 3rd for the data I make and/or manage and the final one is just for temporary file storage. The rationale behind this strict separation is that I take a lot of work out of the hands of the NTFS file system this way. Now it only needs to taker care of finding the ideal positions of files on each partition and afterwards the content om partitions 1 and 2 will barely change.
The file system only needs to do a little content "house-keeping" on partition 3 and the temporary files on partition 4 can easily be discarded, so those files don't matter at all. This structure keeps systems lean and mean, even after years of operation. Many on this forum and real life think I am way too extreme with this divvying up, but I see only advantages. Besides consistent speed, it also makes backing up data much easier.
Anyway, Windows will work fine. You might encounter software that "expects" certain software to be in a certain location, but that is usually software written in a way that is not according to Microsoft's guidelines. Properly written software really doesn't care where it is installed.