I have a Windows 7 laptop just now. Its about a year old. I run Norton 360 on it for antiviral purposes and it also runs an optimisation and cleanup function which keeps things running sweetly. I have never heard of the "pretech file" - not sure why.
One thing I do know is that troubles can happen when a hard drive is full. Makes it hard to run the optimisation and cleanup and defrag functions and if so deleting a large file or two can help in this regard to create some space for such functions to do their job.
I havent come across the duplication of files that you refer to.
