Partition Difficulties and 'System Event Log'

[Thesus]

Okay, I'm trying to install Ubuntu.
The first problem I'm hitting is that I have 27ish GB free, but both the vista GUI and diskpart.exe tell me only 1GB is free for partition.
Okay, fine. I'll make the partition and extend it later.

But when I go to create the partition, I'm told
"DiskPart has encountered an error: Access is denied.
See the System Event Log for more information."

I open up Event Viewer and poke around, but I don't see anything relevant. Advice?

[BertImmenschuh]

Having 27GB free and having free unallocated space are two different things. The 27GB free appears to already be in a partition [every HDD needs at least one partition] and that partition would have to be resized downward to create unallocated space.