Hi, I've got a Windows7 64 Bit system, freshly installed, and WMM 2012. I'm finding that when I import HD clips, the preparation process works as expected, and the saving movie process works as expected, but when I want to edit the project, the program acts very sluggish. I could move the timeline from 0:00 to 3:00 (3 minutes), and it might take the program 2-3 minutes before I can see or play the content that is at 3:00. So editing a 30 minute video clip might 12 minutes just to set a start and end point that is different than the native clip had to begin with, meaning just trimming off a couple of minutes at the start and finish. 

Prior to reinstalling Windows I was able to edit anything as you would expect, moving the timeline anywhere within any clip, even a 3 hour long clip, would give instant response, no waiting as described above.  I don't know what version of WMM I had on the system as it had been editing video very nicely since about 2010, but I would guess that MS was updating it regularly anyway.  No other programs are running slowly on the system, it just seems to be WMM that has this problem. The computer isn't doing anything else, and I've cleared the temp files from the system before hand, that makes no difference.   Task manager will show 45-60% processor usage when the prob is happening, so it seems like it's a huge, processor intensive process for the system to find the newly requested edit point in the project. 

Oddly, every now then (one out of 8-9 projects) the software behaves normally.

Does anybody have suggestions as to how to fix this?  I did have a virus on the system thanks to the Mobo manufacturer's bundled software that I shouldn't have loaded, but that has been removed by MS Security Essentials, and I get clean scans now, and malwarebytes also reports a clean system.  I'm probably going to attempt load W7 on another drive and see if that corrects the problem, but if anybody knows what might fix the prob, it seems like that would be way easier than doing another full install of W7 again.

Thanks for reading and/or helping!