I want to enable time machine but I want to keep my backups on the partition of my 1st disk. But it only accepts my extrenal USB disk.

Is this my only option or I can enable time machine to the partition as well?

If you have only one partition on your first internal HD it won't work. In that case it wouldn't be a backup.

Big external drives are pretty cheap these days - i bought a 500gb usb2 drive for £85!!

They'll beginning at 65 Euro in Germany, so about 100 USD or £51.

I don't want to add another HDD I have already 3 internals and one external 1Tb in total.

@ naquaada

I have 2 partitions in my 1st hdd in the 1st partition I have Vista which I will erase and on the 2nd I have Leopard and I want to have the 1st partition for Time machine. But it want let me use it, it doesn't even shows my other 2 internal hdd as an option.

Maybe TimeMachine wants you to use another harddisks. A backup will only be worth it if it's on another storage device. If you make a backup of partition 1 to partition 2 and the HD will hard crash, the backup was no use at all. If the Backup is on another drive the data are safe.

I just tested it, I get a message which asks me if I want to make the backup the data on the same harddisk I'm using. But I've got 10.5.1 now, maybe they don't allow it in 10.5.3 at all.

But it doesn't let use not even the other 2 internal disks, as an option I have my USB disk.

Hm. But anyway - I tested it and in my opinion it's crap. 'cause it's updating all the time you'll have a lot more hard disk access as usual. Think over if you really need it - and not only because it's a cool component of Leopard.