Yes, but you are required to specify in your documentation (1) that you used parts of the 7-Zip program, (2) that 7-Zip is licensed under the GNU LGPL license and (3) you must give a link to www.7-zip.org, where the source code can be found.
What do you mean when you say "attempted to extract it"? Did youextract it? What did you use? Did you get any messages?A "7z" file is a 7Zip archive file (www.7-zip.org), so if your file isstill called that, I'd be curious that maybe it didn't extract.You should have a .vdi file, which is the hard-drive from a VirtualBox machine.