How to fix bootcamp glitch - cancel sign and question mark during reboot???

Ok so I am on a mac mini mid 2007 running OS X Lion. I am trying to install windows 7 on it with bootcamp. When I go on bootcamp there are just two options, not the option using flash drives and iso files. So I edited the info.plist to get this third option. I didn't have a flash drive so I used an external drive and a windows 7 iso file. I selected the partition, everything was going well until it restarted. As it restarted, after the startup noise there was a grey screen with no apple logo. After about 10-15 seconds the apple logo came, but was, every now and again, changing with a cancel sign (circle with diagonal line thru it) and an icon of a folder with a question mark in it. I left the mac like this for about 2 hours and nothing different happened. So I switched the mac off and on again. Then comes the screen saying there is no bootable drive. So I switch it off again and when I turn it on I hold down the option key. Then there is only one option, macintosh hd and not the bootcamp partition drives. I select the macintosh hd, come back, delete the partiton and repeat the whole process - same consequence. I even got a different windows 7 iso file and still nothing. I made sure I was on admin and did software updates, sometimes I installed the windows support software, sometimes I didn't. I tried many different things but always came back to the same consequence.

If someone gave me a solution I would be extremely grateful. I REALLY NEED Windows on my mac and I need it ASAP. I tried virtualbox but it was too slow. Parallels was the same.