Recycle Bin in Windows 7 has been adjusted for user ease, to see and adjust the amount of space currently used by the Recyle Bin for each drive that it protects, right click on Recyle Bin and choose poperties. In Recycle Bin properties dialog box, you can select a drive and enter a different value in the custom size box.

Windows ordinarily allocates up to 10 percent of a disk's space for recycling. If you don't want to allocate Recycle Bin for a particualr drive, select the drive in Recycle Bin location and tick don't move files to the Recyle Bin, Removes files immediately when deleted as shown below