My sandisk M2 4gb disk crashed

Your card has most likely become damaged or corrupted and you will need a data recovery application to try and pull the pictures off of it. I recommend the programs from http://www.runtime.org/data-recovery-products.htm I have been using them for years with great results.

What you will want to do it get a product like GetDataBack for FAT V4.00 assuming your sandisk card has a fat file system (Which it should). Once you have your recovery app installed you will then load your card into the card reader and plug it into your computer. Open up your recovery app and it should allow you select the card reader or the card itself. The recovery app will then do a low level scan of your card and attempt to pull any data it can from it. This process is honestly hit or miss, but it is really the only chance you have at home for recovering data.

If this fails and you really want your data back there are recovery companies like On Track that you can pay to retrieve your data. They have VERY good odds of getting your data back, but their prices are a bit high.