if this is a brand new computer/setup do you have problems with any other programs or just isolated to premiere pro? have you by chance ran any stress test software to verify the hardware is working ok? im not sure of the exact problem, but do you have any firewall or other security programs that are blocking apps by default? adobe uses network ports/communications to talk to itself inside your computer, if you have a firewall program blocking these it will cause problems. you can try the usual windows tricks, run the program as administrator, log in as another user, turn off user account control, and/or disable non-windows startup programs.
also have you tried other files in another codec format? does premiere do the same with them? premiere should be able to handle WMV format even though its not a good codec and should be avoided where possible. also your video card is really underpowered for your cpu. it should handle wmv fine, but with multiple videos in multi-cam format it might slow down here and there. im not saying thats the problem here, it sounds way worse than a slow video card, but in general a gtx 960 or 970 would match your cpu better, as premiere pro does use the video card alot to run.