Re: PreFetch + Temp folders
If there is malware in them, that is because you, as the user and weakest link, did not practice safe computing.
The prefetch works by learning your computing habits and over time, configures itself to load your favorite programs faster. It serves no purpose to delete the prefetch because it is constantly self adjusting.
The temp files are as mentioned and many programs use them, including Windows. Over time, many temp files can clutter up your hard drive, consume lots of space, and contribute to fragmentation. Periodically cleaning your system of temp files with Windows Disk Cleanup or a program like CCleaner can help keep your HDs tidy.