crashesblue

I bought my 1st p.c and the config is as follows: mobo: asus m4a78lt-m le pro: amd x4 635 gcard: hd5670 1gb ddr3 ram: 4gb 1333mhz ddr3 corsair mercury psu: 450w. I tried to overclock but the windows wont boot up even if i increase the o.c 2%. it just crashes(blue screen with some error)...