Serious problem with fan

I have an Inspiron 600m and I am having a serious problem with my fan. Almost every time it goes on, it makes a very loud grinding noise, and I have to shut off the laptop every time it does that. I believe the reason this happens is because of something I used to do, which was probably pretty stupid.

At night when I went to bed, I flipped the laptop upside down and put a jug of water on it to keep it cooler overnight, because I like to keep it on all the time and when I did use the jug, the laptop wasn't sluggish in the morning because it was cooler. However, I believe flipping the laptop over like that unbalanced the fan or something, and it has really had problems going without making that loud grinding noise every time it starts up.

That said, I have tried removing dust from the fan by basically blowing on it really hard when it's off, because as suggested in another post, this could unbalance it as well. In short, the fan wouldn't even start up as a result. I have a temperature reading utility that tells me how hot the processor is, and I notice whenever it goes above 120 degrees fahrenheit, it always kicks in. But when I started it up just recently, the temperature was up to 180 with no fan going at all. Does anybody have any suggestions or should I just see if I can get a replacement fan?