I don't need a harddrive, but I need my phone to act like one.
If you needed your phone to 'act as a harddrive' you should've bought one that had this feature. As I said, the iPhone has never had this feature, nor claimed to have it.
I also have two computers, and when hooking up one after is has not been used for a while, it erases my music on my phone if you haven't been smart enoguh to transfer the music folder.
iPhone is primarily designed to be synced to one computer. This is by design and has been known about for years. If you want to sync with multiple computers, manually manage your music, don't sync it. Read: http://support.apple.com/kb/ht1202
iTune is used so Apple can control what you are doing with our own property.
You might have purchased the phone, but you don't own the operating system or the other software used to operate it. You are licensed to use it (like most software). If you didn't agree with that license, and the features the software provides, why buy the product?
You should've done some research before parting with your money and bought a product which better suits your needs, instead of whinging when what you bought doesn't do something it never claimed to do.
the problem is that iTunes dos not work on one of my computers (Win 7 Professional, 64 bits).
Have you downloaded the 64-bit version of iTunes for that one computer it doesn't work on? See: http://support.apple.com/kb/DL1615