Not Enough Video Memory for Coherence

I've just upgraded from Parallels 4. I now got a message that tells me that it is unable to switch to coherence mode as the amount of video memory set for this virtual machine is to low. Resultingly I now get a tiny little screen in which to work on the windows side.

Can you please tell me how to increase the amount and by what. Also, please let me know if it will impact anything on my Mac side.

I sent this to support almost 3 days ago and still awaiting a reply, so hoping some other helpful person here has an answer for me.

Thanks
Shelley