Firstly thanks for your response weinstein5 No I'm expanding G drive which only contains shared folders etc...
Here is our the current set up
DISK 0= 100 GB only one partition which is C drive
DISK 1= 300 GB 2 Partitions G:200 GB 99% used H: 100GB 84% used
so G is running out of space I edited the vm disk 1 setting and made it 400 GB.
Now i can see 100GB unallocated space but can't expand G drive get an error, However when I try to expand H drive it works fine, so why it fails when both partitions uses the same disk