Okay, so I have Foobar2000 installed, Installed the QAAC and also iTunes which was not previously installed. I do not see AALC listed in the convert window.
Do I need to reinstall Foobar2000 after having installed iTunes?
As I said before, I don't use Windows as much as Mac but the process works the same using iTunes in both systems. I never mentioned Foobar and you don't need it if you use iTunes. You said you have the files in AIFF format so the following will apply to that. I still use an older iTunes 10.7 version as I like the CoverFlow format but newer versions work the same.
First, after installing iTunes you need to add your music folders from the File menu. I just added a few for the screen shot. These are AIFF files:
Then, go to your Preferences menu under Edit and go to Import settings:
Select the one that says Apple Lossless Encoder which is ALAC:
Now, select the tracks you want to convert by highlighting them and to the Advanced menu and you will see the choice of Create Apple Lossless Version. That choice will change depending on what you set in the import preferences mentioned earlier. So if you didn't change it at first, it is usually AAC so you must select the one you want in the import preferences:
Once you do that, iTunes will start converting the tracks and you will see the new ones listed under the original ones:
You can check that the new track is Apple Lossless by selecting it and getting the Information under the File menu. Apple Lossless files do not have the same bit rate like AIFF:
As you can see from the last screen shot, it tells you it is an Apple Lossless file as well as the fact that it was converted with iTunes. Notice it indicates where it stored the files. That is usually the default media folder but you can specify the location before starting this process. For example, my AIFF files are on a separate drive from my ALAC files and mp3 ones. When you do the conversion in iTunes, it will place the new files in the media folder you specify in the general preferences. I hope this helps you in the conversion process.