Hmm maybe it's just me but..., when you purchased DXC Xpress surely you saw that the staple ingredient to it's usage is a dvd burner?
You see this program will not function without one, now you did say you purchased it yes? Only I am confused at the way you say you downloaded it and it's the first time you used it.
Anybody who purchases DXC, DXC Xpress is give a link to the DXC support forum and yes I know there's a 48 hour cooling period. This is solely to get new members(and customers) to familiarise themselves with the forum and seek out information before posting an already answered query/problem.
Now back to the question 5gb is insufficient.
I've posted it before, but here it is again. The DXC support forum.
http://dvdxcopy.afterdawn.com/