Swap hard drive windows not booting

[yesterday]

I found an old pc in my basement and I thought I would try to restore it and use it as media pc. The PC was without a hard drive and an optical dvd drive (only cd's) so I got a hard drive. I wanted to install windows 7 on it, so I connected the hard drive to my pc I use normally installed windows on that and it booted fine and worked nicely.

Then I came to swap the hard drives so I put it back into the old pc once windows was installed and I got errors, I could not boot up. I checked RAM, made sure everything was seated correctly but nothing. It then asked me whether I wanted to do a start up repair which I said yes to but once it had finished the repair I got the message:
'Setup repair cannot repair this computer automatically'. I looked in the logs and the error codes all were 0x0.

What can I do now?
Thanks

[Allan]

You cannot install windows on a hd on one system and boot to that hd on another system. You have to format and install the OS on the system you want to use.

[yesterday]

So how can I install the os on the old computer when it has no dvd drive. I have a spare dvd drive but that is sata and the computer only has ide. I have a pci convertor card ide to sata will that work, I thoguht it wouldn't because of driver issues? What can I do? Thanks

[Allan]

Your first post is a little hard to understand - does it have a cd drive or not? If it does, you can install an Windows version that is on CD (ie, XP). If the system is that old, the likelihood of it being able to run Windows 7 is pretty slim anyway.

[yesterday]

Sorry I will try to be more clearer.
It has a cd drive but not a dvd drive hence inability to install windows 7. I only wanted to install windows 7 so it would be easier for it to talk to my main computer and I only wanted to use simply to run xbmc. I guess i could try win xp but I really wanted win 7 on it.

[Allan]

1) Without a dvd drive you cannot install W7
2) If it is an old system you don't want to even try W7
3) Your license for W7 is for 1 system only - but given the situation, it really doesn't matter