If you have downloaded apps to the hard drive of your PC and installed them, the apps should be right there in the hard drive.
If you downloaded app through YouWave's Android side, the apk files are inside the file <user>/.Virtualbox/Harddisks/youwave_vm01.vdi. Save a copy of this file because all your data and apk files are there. There is a third party application Winmount that can copy files out of this file. Alternatively, you can install Dropbox app and copy files out to your Dropbox folder.