problem with partitioning HDD

Hello!
I have 2011 mac mini, i5 with discrete graphic, 8GB RAM and 500GB HDD.
it runs on Lion.

I want to install win7, but I can't partition my HDD because it opens error message like this:

Click for large view - Uploaded with Skitch


however, I have tried to partition disk with disk utility, and it won't work also:

Click for large view - Uploaded with Skitch


then I have booted in recovery mode and ran disk utility there, used all techniques (verify disk permissions, repair disk permissions, verify disk, repair disk) and although it returned some info that I have to repair disk (and I did that afterwards, then it showed no faults in disk) it still won't partition. does anyone have an idea what to do, I am desperate to play GTA San Andreas WITHOUT bloody lag like in Mac App Store version.


thank you all for your help, sorry for my english, but It's my second language.

 

somehow I have managed to partition HDD, but now it wont install win7.

I'm installing from USB key, windows file is illegal (but working) (illegal is because I don't have DVD reader for mini to install my authentic copy)
but it wont boot. it stays @ black screen where one grey "-" (without quotes) blinks for infinity.