Digital cameras record the image using a CCD that converts light to analogue signals, which are then processed in the camera to create a digital image. You can adjust the sensitivity of the CCD so that it increases in low light allowing it to record the image. Unlike a film camera the ISO can be adjusted automatically so you don't have to decide which speed to set just point and shoot. In low light the camera will increase the ISO to ensure the photo is recorded.
Like increasing film speed you do have drawback to upping the ISO of a digital camera. The higher the sensitivity, the more likely pictures are subject to noise, which appears as randomly-spaced, brightly coloured pixels. Most digital cameras have an automatic sensitivity range of between ISO100 and ISO400 and some have a manual override. Some go up to ISO1600. The beauty with adjusting the ISO of a digital camera is that you can check quality on the LCD preview screen and reshoot if necessary. This is easier if the LCD has a magnifying option as it's hard to spot noise on a small non-magnified version.
Or in other words you should check the camera to see how far you can adjust the iso level, i know the DSCV1 has a manual setting not sure about the other one, a quick google should tell you.