Doctor Who wrote:I’ve got an old PC, which has a failing C: drive in it. This PC has only 512 MB of RAM, and it is expensive RAM so I don’t want to upgrade to 1 GB. It also has a second hard drive, as the D: drive, which works fine. I am thinking of installing XP Pro onto the D: drive. What I’m wondering about is will there be a problem making this the primary drive, especially if the C: drive fails me completely? I believe there is a file called BOOT.INI which lists the hard drives and which one is the primary drive, etc. My guess is that BOOT.INI is on the C: drive. If C: fails, then won’t that make it impossible for the machine to know which is the correct boot drive?
What does RAM have to do with it? I think you're confusing yourself here. As for expensive RAM, it probably was expensive at first. You can probably get 1GB for the same price you paid. Also, how do you know the HDDs broken? I've seen many cases where people claim their HDDs are dying, and they're running high perf applications on little RAM.. might be the same problem.
You can install XP on the D drive. Go for it. Just make sure you've got your stuff backed up.
As for Boot.ini, that's not my "field", per sé. It is my understanding that should you have XP installed on D, and C failed, then the PC wouldn't see C and would just jump straight to D. Once you install XP onto D, you install Boot.INI there as well, so it would initialize as usual. I think
Install XP on D, open your BIOS (press F2, Esc, whatever it says to "enter bios" or "enter configuration") and set it as the default boot drive.