I just append -vm C:\\Program Files\\Java\\jre6\\bin\\javaw.exe
in ec
You need to check if your PC has a 64-bit or 32-bit operating system, then same goes for your JDK (64-bit/32-bit) and also for Eclipse (64-bit/32-bit).
Make sure they are all the same; if not, you need to download the one that matches your bitness.