All Linuxes recognise practically all file systems however you will need to delete the 30GB partition in Win7. Otherwise there may be a problem within Win7.
Download whichever Linux you want to install Ubuntu 12.10 is good, once you have made a few minor changes to it. Look at the instructions on the website; once downloaded you can load from inside running Win7, or boot it from a USB or CD. For the latter you may have to go into boot device selection at boot up time [F8 for my mobo].
The loading is absolutely straight forward for Ubuntu, with a few things to select but not much. The most important thing is get the right area on the disc, the blank bit, not your Win7! This is a specification right at the beginning of the process.
It may suggest that you load Ubuntu into the Win7 partition but you don't actually want that. You want to specifiy the 30GB area, also specify a separate SWAP partition, equal in size to your RAM, or 2Gb, whichever is the smaller. You do not format the swap partition but you do format the Ubuntu partition into EXT4.
Once you have the swap and the Ubuntu partition, it will load itself into what remains of your 30GB. The new bootloader will recognise Win7 and Ubuntu [and anything else] and needs to be installed into the Disk MBR (master boot record).
From now on the boot menu will have Ubuntu as default, plus an optional Win7. You can change this arrangement at will, in Ubuntu if you load up Grub Customiser from the web.
The MBR is now controlled from the Ubuntu partition. If you load Win7 again, it will over-write the MBR and you will have lost your way into Ubuntu.
Don't panic you can go through the motions of re-loading Ubuntu and the MBR will reset itself.
Windows recognises no other OS and must be installed on first partition. You pays your money and gets no choice. Linux is perfectly flexible.
In the unlikely event of you running out of primary partitions (4 maximum), you will have to extend the partitions using primary partition 4. Win7 only recognises primary partitions - up to a certain point; it will not be able to read the Ubuntu partitions, although SWAP is not readable anyway! Ubuntu will be able to read all other partitions, once they are "mounted".