for resizing program and you're on XP, google windows powertoys and you'll find an image resizer that works by just right clicking on the photo and it appears in the pop-up menu.
for not getting your images overexposed, it's not one specific setting. using bulb keeps the shutter open for as long or short as you want and you have to judge how long you need (trial and error, then eventually experience). If you want to lengthen the shot as long as possible with the least amount of exposure, stop your lens down (large f-stop number) and turn your iso to 100. you could also add either a neutral density filter or a polarizer to make even less light enter the lens, and thus allow you to increase your exposure time.