1. If you can find what brand it is (might say on the front), or if your computer is a specific brand / not custom (IE: Dell, IBM etc.) you might be able to find some drivers on the manufacturer website. Mine does a similar trick...except no error messages. It starts off kind of loud, then becomes silent... I don't ask questions
Also, you might try using a different burning program... if you haven't already.
2. Partition Magic is a nice GUI-based program...that you'd run from Windows, if you can get a hold of it. I just googled a freeware one, though no idea if it's any good here
. You'd be best off reformatting since it sounds quite messy...(reformat/split partitions/install again), though if that's not an option, resizing should do what you want--but in order to split it up into two seperate partitions, I do believe you will need to clear that space (resize the 30GB to 15GB (this data you keep), then create the new 15GB partition).
Hope that helps...!