Are you sure it's Outlook 2010 that you are using? If so, are you sure you are looking at the right PST file?
1.9GB is nowhere near the maximum file size for a PST in Outlook 2010 - maximum is 50GB. If it were 19GB that would be close to the limit in Outlook 2007 and earlier (20GB).
It is possible to increase or decrease the maximum size of the PST in the registry, so it's possible that it has been decreased at some point to 2GB.
I'm using Outlook 2010 and the PST containing the inbox is 3.5GB. I archive stuff at the end of each year to a year.PST, so it will be reducing shortly! My other half has a 6.6GB PST, despite my suggesting archiving...
As PPRuNe Dispatcher says, you can easily create new PSTs and have them open in Outlook however you want.
But Outlook reporting that it's approaching the limit at 1.9GB is possibly indicating an underlying problem that you need to investigate.
SD