with the 1000d there should have been a CD in the box which contained the EOS Utility program. Install the software from here if you haven't already. Plug the camera into the computer using the supplied USB cable and fire up the EOS Utility, it'll display a menu. Click the blue square (control camera) followed by Camera Settings/Remote shooting. This application will allow you to view the same image as through the viewfinder (or liveview on the rear display) on the computer screen, far larger and easier to see. You can also zoom in 10x (iirc) to check fine focus. All the controls that you'd change on the camera are available, so if you're in manual mode, you can change aperture, shutter speed/iso/white balance etc. There's even a facility for pulling focus, provided you have a AF lens attached and switched on AF rather than MF.
I use the tethered shooting a fair bit, mainly for product shots/macro work where being able to see a highly detailed screen preview is a great help. As an added bonus, the shots you take go direct to the computers hard disk so you can keep shooting as long as your batteries last without filling the SD card.