Hello everyone. I am new to this forum, just had a quick question: I did a recording yesterday and my audacity developed an error. I located the .au files in the temp folder and saved them on the desktop. My question is: How do I merge these raw files together again in audacity? I would really appreciate your help. Thanks. 
What sort of error?
Manually rebuilding Audacity Projects from the .AU files is not always possible. Normally you should not mess with the .AU files and leave them to Audacity (Open the .AUP file).
In the case of an error, Audacity will usually automatically recover the project the next time Audacity is restarted.
If auto recovery fails, then it may be possible to recover the recording from the .AU files provided that it was an un-edited recording. The .AU files need to be recovered in time order, but editing or processing cause the file creation times to be out of sequence.
If automatic recovery has failed on a project that has been edited / processed, then I hope you have a back-up because manual recovery is probably not going to work.
See here for more information: Audacity Manual