I was trying to boot my Backtrack 5r3 VM off a boot CD (.iso file) instead of the hard drive so that I can re-partition my disks, and even though I knew I had to press ESC at boot to get into the Boot Menu, I could never catch it quick enough and it would just boot off the hard drive each time.
There isn’t anywhere in the VMware Workstation settings (and Player too I assume) that controls the boot delay.
It turns out this can be configured however by adding an entry to your virtual machine’s settings file (the *.vmx file located in your virtual machine directory). The entry to add is:
bios.bootdelay = 5000
This will show the boot options for 5 seconds, and allow you press ESC and then select that you wish to boot from CD.
Once in the boot menu, you can also access the Settings area to change your boot order permanently, so that whenever you mount an .iso or CD it will first try to boot from it (optional).