If the Power Supply Unit nor Motherboard did come with an additional +12V connector (4 pinned) you should consider buying one that does.
Not sure what it looks like, is that the one with two pin slots in two rows and the top has a clip? Not too sure what it looks like on the mobo either. Any benefits to this?
If you are into DIY, you may be able to repair the mainboard by replacing the main power connector. I would advise against this, though. Especially if you consider using the same Power Supply Unit. It's probably not all that safe.
No way, that's out of my scope and its sounds difficult. The damaged atx connector on the power supply is probably unsalvageable. It was a 350w powersupply but I plan on getting a 400+w.
You can mount it as a slave in your sisters computer and transfer the files.
Not sure if that's possible. Her main hdd is almost full and she runs Win ME.
Will things still work out if I mount that same xp hdd as a slave if I install Win 98 on that spare hdd(making that one the master) I was talking about earlier? Will I still be able to transfer the files I need in that case? Dusty also mentioned file system compatability which has me extremely worried.