I tried today to get VirtualBox set up on my Linux (Ubuntu 7.04) box at work. WinXP installed without a hitch, but it refuses to install Visual Studio 2005, which is the only reason I wanted to run WinXP in the first place!
Here's a screenshot of the error
A google search on the text of the error message returned no hits. The Properties menu says I have 14.6 GB of space left on my (virtual) hard drive, and Linux has plenty of real disk space left, so I don't think that's the problem.
VirtualBox seems like an excellent product, and responsiveness within the guest OS seems quite snappy, so my current state of affairs is disappointing.