I need help troubleshoot a Dimension E310 startup.  PC will boot and show accounts in login screen.  When you choose any account, I get message that personal settings are being loaded, then it would logoff and show login screen again.  This happens whether in safe mode or normal Windows startup. Also, Windows OS will not boot from internal DVD drive even after changing the BIOS to run DVD first.. I also tried installing a USB extenal DVVD, external drive jsut keeps spinning. Green power lights stays green all the time.  Before all of this happened, I suspected a trojan virus infected the PC.  I was able to remove "some" virus, but now PC will not boot correctly.   Thanks in advance.