What model of camcorder is your video coming from and what format is it?
When you set up your Premiere Elements project, which settings did you select?
What operating system are you working on?
How fast is your processor, how much RAM do you have and how much free, clean, freshly defragmented space is on your C drive?
Are your project and media files on your C drive or on a second or external drive?
If things are working well, just after a reboot, but then slowing down, or stopping over time, my first guess would be that you have programs and processes open and running (though you might not be aware of them), that are sapping resources, until the system begins to run low. I'd take a look at this ARTICLE, and see if there are many processes, and programs, that load at boot, that could be using the resources.