Yas1EC, learn an important lesson from this: ALWAYS backup. DVDRW's are very cheap and you can store loads on them. Use Windows backup, or there are a number of free ones out there (Peter's backup is one I used a while back) and even some online backups, although you don't get much space for free. Remember "Data isn't safe until it exists in three places". You can even use xcopy/m for incremental backups.
Colin's right though, if you've done it once then you'll be able to do it again. It won't take you a month second time round cos you'll have learnt loads from doing it the first time.
Don't expect sympathy from your lecturer. He'll have heard all the excuses for not handing in homework on time, and he has no way of distinguishing between the truth and lies. If you really had a computer crash that lost everything, well it happens, but that's what backups are for. You may be able to get an extension if you can prove it is true, but the chances are your college has already explained that you need backups and may already have made provision, so you might just have to accept a zero score for this assignment and prove by the rest of your assignments that this was a one-off.