My Computer

So last Thursday the fan on my CPU started to make a grinding noise. I got figured it was due to dust buildup in the case so I opened it up got out a can of compressed air and blew the dust out. I restarted the machine to only find that the sound was still there. So I turned it off again and this time pulled the fan entirely off the processor to clean it separate from the rest of the machine. After I felt I had cleaned the fan out sufficiently I replaced it again only to find that it still sounded like a I had a meat grinder in my tower.
Now my computer is the Frankenstein's Monster of computers. I got the original tower when I went off to college as a graduation gift from my parents and grandparents. My mom who bought me the computer was lied to and swindled by the company she bought it from. Now I went to college in 2001. The computer I got had windows 95 on it, a no name processor, 64mb or ram, and no modem or LAN card. oh and a 5gig hard drive. My mother told me she paid over $1,000 for it. So over the years since I was a college student with no money I have been "fixing" this computer whenever I can get my hands on old parts from friends and co-workers who happen to have a computer that they no longer want. I have been able to switch cases once before about 2 years ago and I have picked up 2 new hard drives, I have purchase and acquired new RAM as well as video cards and network cards. But now with this fan starting to fail I am thinking it is time now for me to lay this beast to rest.
I would like to finally have a machine that is not 5 years behind the latest technology. However if I have gotten one thing out of working on my Frankenstein machine it is this; I can build my own computer. So now the dilemma I have is purchase a tower and build a PC from scratch for around $350 for the tower and then add vista $150 and Update Word for another $100 making my build my own machine cost me $600 or just go out and buy one from Best Buy for like $900 with a monitor. Now while either machine would do what I want I think I am leaning to building my own, because beyond the starting cost of buying the parts I need the software could be picked up over time.