Seems to be USB driver problem.
Have you installed all the latest motherboard drivers including USB drivers??
Try unplugging the printers & plug them in other ports.
Have you installed printer drivers for both of the printers, if not so, do them first & try again!
For your HP printer, download the latest drivers (select 32/64 bit Win7) from here
http://h10025.www1.hp.com/ewfrf/wc/softwareCategory?lc=en&dlc=en&cc=us&product=3635378&
For Epson printer, get it from here
http://www.epson.com/cgi-bin/Store/support/SupportIndex.jsp?BV_UseBVCookie=yes&oid=-10222&infoType=Overview
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