It's one of those stupid defaults that is set based on the size of the hard drive.
If you use a broadband connection then I would set it at 10MB (that's what I use). If you use dial-up set it somewhere between 50-100MB.
Another thing to check. If you right click on the Recycle bin and select properties you can see how much space is set aside for it. The default is 10% (on your hard drive that would be 12GB!). Set it to the min 1%.