You should be able to. Save the Windows library as a file onto your Mac hard drive, open iTunes then under the file menu "Add to Library' or "Import" to the iTunes library. Hopefully the dialog boxes will be friendly and tell you what to do.

In the iTunes preferences under 'advanced-general' check - copy files to itunes music folder, etc. and under 'advanced- importing' check - import using AAC encoder and uncheck - play songs while importing.

Good luck, PM me if anything else.