I've installed Mac OSX 10.9 Mavericks on virtual machine. It took too much time & efforts
to install and after that I'm experiencing the slow & sluggish behavior 
of the guest OS. Also tried reinstalling the Virtualbox and guest Mac also 
. But it didn't solved my problem. 
Secondly, I'm unable to manually resize or set the screen size/resolution of the guest Mac
. 
I searched for it on the internet and 
followed all the tutorials to change the screen resolution to 1366x768; 
inside the guest Mac and also with (CMD) elevated command prompt on host Windows 8.1. But no changes occurred. What should I do to solve these obstacles.
Please help someone. 
Thanks in advance.