Problems updating my MacBookPro 2007

Hi,

I'm trying to update my 2007 MacBookPro to Maverics or Mountain Lion but I cannot get it from the Apple Store because it seems to be too old.

At the beggining it was not a problem for me (my current version is 10.7.5 and it works properly), but now I need to download some apple software (Xcode) and the only source I've found to get this is AppStore, that denies me the program cause it has only the very last version of it (which runs only in Mavericks)

I supposed there must be many people with the same problem..any help?

Thanks,

J.

PS. My Mac is 2,33 GHz Intel Core 2 Duo, 4 GB, 667 MHZ, 500GB