If you can afford investing in a new machine at this point I would. The improvements made in the other components that makeup the computers today are so much better than in 2007 I think you will be wondering how it is you got along this long. If you can't, then paying 400 to get it back on it's feet is actually not too bad. But just like a new transmission for an old car, you have to consider that is probably upwards of 30 of the cost of a new one.
Without seeing what the rest of the computer looks like, I couldn't tell you if the other pieces besides the drive are going to keep you going for another year or two, or if the whole thing is about to give up, taking your 400 along with it.
 Tesla tried to sell his idea to the U. military as a type of radio-controlled torpedo, but they showed little interest.  Remote radio control remained a novelty until World War I and afterward, when a number of countries used it in military programs.  Tesla took the opportunity to further demonstrate "Teleautomatics" in an address to a meeting of the Commercial Club in Chicago, while he was travelling to Colorado Springs, on 13 May 1899.