It is not really that difficult. If you have a Sata to Pata interface (I have one sitting next to me) that requires a molex and not a SATA power connector and it is losing power, then you you need:
1) A tighter fitting molex -> which you can get on a new PSU.
2) A molex to Sata connector (sitting next to me too) but you might have faulty molex sockets that can hinder your efforts so go to 1
3) A Sata power connector -> which you can get on a decent modern low cost PSU.
Like Shmokes knows. Faulty hard drives are bad news. Trying to create a problem where a drive can go bad is not a good thing, especially if you being cheap.
Better to buy a PCI Sata card and a new PSU and resolve the issue, than going cheap and having to restore your arcade drive. That is if you have backed it up already.

Shmokes wants me to defend my argument. Simple risk analysis. No degrees here just experienced work as a field technician for over 20 years. Fix it fast, fix it right.
I had the same problem. I bought several Buffalo External Drives (640gb) and decided that I had enough with power bricks and USB cables being littered all over my desk. So I cracked open the cases and mounted them in my development server. The problem being the abundance of PATA interfaces and no Sata. I should follow my own advice and buy a PCIEx1 Sata card, but the drives are used as storage and rarely activated, and I opted for the PATA to Sata interfaces with the Molex power.

No I go for the Pata to Sata and it worked very well until things started to go pear shaped.
I got problems with the connectors too. Reboots etc.
I just got a new mainboard + CPU that has oodles of sata ports to replace this ageing behemoth which will go into my Weecade.
Don't mess about with your data. It is so easy to lose it and when it is gone, it is very hard to get it back.
