How can i save up for a good computer?

Well, I;m only twelve and I'm pretty lazy with saving money but i've gotten the hang of it. My MONTHLY income is about 50$ and month for doing the paper run every friday. (puting papers in people mail boxes) and i have about 50 bucks in there now and the computer i really would like is around $800 - $750 dollars and i was hoping to atleast save up $700 then have a little help from my mum and dad. The PC i want is pretty good, it has a lot of storage and that's basically what i need. My laptop right now is a silly laptp that out school provides for us. (well we pay for it and they give it to us :|) and it has a HOME and SCHOOL setting. And on my home it's pretty sucky all i can do is go on the internet, watch movies and play only like 1 game thats 3-D. I really want a good PC that i can play games such as MapleStory and Paintball, Halo on. I had a really good Gaming computer before but it died because i was too careless with the anti-virus system. But i know ima save up more money for buying a good anti-virus thing. :D But yeh, and i dont really want to do any "neighbour hood" stuff cause my neighbourhood isn't really the most polite and bright one. People here are really strange and mean soooo- yeh. and yeh when im like 13 and 1/2 then i might be able to make more money with a job but i cant really wait for next year. :[ (im not very patient lolz) I've all ready waited a year for my parents to finally have the heart to consider getting me a fairly good PC LOL! but now I've decided that Im'a do it my self! >:D *thanks in advance guys!*