Digital IXUS 700 capturing dark pictures...

[dfs3000my]

I juz bought this camera and started taking lotsa pictures. All pictures seemed to be perfect till I realized that certain pictures that i took is exceptionally dark even though the actual area was quite bright. All these happens whenever the flash mode is on. I know that the digital camera will auto-adjust the brightness of the area but not until it is totaly dark! How can I rectify this problem? I tried increasing the ISO but the picture will be filled with noises. Another problem is whenever i turn the flash off, the camera will appear a icon which symbolizes 'shakey camera'. I really don't understand. Can someone help me out here?