Uninstall your antivirus, you can re-install it after the upgrade. Also go at Control Panel, Device Manager and disable any non-important device (audio card, any SATA or SCSI controller that has no drives connected etc). Press Win+R to open a Run prompt and execute msconfig to open System Configuration. Go to Services tab and check the box to hide all Microsoft services. From the remaining services check the box to disable any non-important service such as updaters. Click on the Startup tab and click to open Task Manager (if no applications shown). Disable any non-important application (Skype, QTtask and others). Then try to upgrade again.