There are a couple of things that i can think of you can try. Firstly, you could always go for Microsofts own video editor, and then choose what type of recording style you want, it then tells you how big each type of file will come out, or, you could simply record the tape to your hard drive and then compress the file once you have finished saving it, this will then save you space on the hard drive but let you keep the quality of a bigger file.
Hope this helps.