I just append -vm C:\\Program Files\\Java\\jre6\\bin\\javaw.exe
in ec
I just hit this too. Turns out that at least for me, this was due to trying to use a win64 version of the JRE with a win32 Eclipse. I seems that win32 Eclipse requires a win32 Java (what is called -586 in the list of Java installers from Oracle/Sun).
The reason I was using both is that I was trying to pinpoint a bug that only manifested itself in 64-bit Eclipse, so I needed a 32-bit to compare to.
Once I installed BOTH the "x64" (win64) and "i586" (win32) versions of the JRE on my machine, things work fine and no error 13. You can apparently have both installed at the same time.