Hmm, weird you say you have a partition ready for windows to be installed on. Does this mean you already have a partition with files on? I'd guess so.
Does it read the drive when the computer is listing the devices in in bootup? It should appear as a Master. If not, this will be your problem. If it appears as Slave, take the hard drive out and make sure the hard drive at the back has the jumpers set to Master (should have a diagram) and also check that you have the Hard drive in IDE1 and all your CD drives in IDE2 though this won't cause it not to work. Its just the default way.
Hopefully after you have checked these, it will now list it at bootup as being a Master drive and windows should read from it.
If its not listing though, it'll definitley be something to do with the connectors, though try this too:
Go into Bios (del at bootup) and check like Rdcmmnst says that the hard drive under the first menu is set to be read after the CD rom is, just to be sure, as if its not listed as a bootup liek this:
First Boot: CDrom
Second Boot: IDE1 Hard drive (or something)
it might not find it when windows is setting up.
I hope this helps