Other - BootCamp Error!!! "please help"

I installed bootcamp in my imac & it was simple I read the instructions before installing it. It ran smoothely I mean vista. But my macbook sucks its graphics card is intel 250mb harddisk 250gb. Now I want to install windows in my imac atiradionHD2600 4gb ddr2 1tb hardisk "space availble 80gb!!!!" I can remove unimportant files to let at most 150gb left "if needed". anyways I tryed to install vista using bootcamp but it said please format using disk utility. I restarted my imac with DVD inserted & formatted it with disutility by pressing alt then choosing disk utility the disk is ok it doesn't need to be repaired it asks to format it as mac os extended journaled!!! but its already mac os extended journaled!!!! so what does it ask!!!!!
I had this error before & just figured that there was a disk error need to be repaired. after fixing it it said "no space available!!!!" though I have 150gb. but then I installed parallels & it worked fine after few hours I discovered that it read the graphics card as parallels video adapter!! which is a problem since the games require known graphics card atiradion or nvidia. now I tried to make a bootcamp partition the error came back again "format to mac os journaled!!!!!"full stop this is where I am standing do I open diskutility by pressing alt while restarting but then what!!! its already mac os extended journaled! So I'm really stuck"

I know this is a bunch of junk words etc but I really want to install vista via bootcamp so what should I do how do I fix it?