I have an old but serviceable Dell Inspiron 600m with a failing hard drive. The hard drive controller is IDE. I would have a lot more options (larger hard drives, SSD) with SATA. I see SATA to IDE adapters available, but I wonder whether they would actually fit in a laptop. As is typical for laptops, the hard drive is not cabled. The hard drive enclosure is built to a specific size, so that a 44-pin 2.5 inch drive plugs in exactly to the receptor. I expect that sticking any adapter between the hard drive pins and the female port will make the drive/enclose not fit. Does anyone have any experience making something like this work?
I doubt you will be able to fit SATA drive, plus SATA->IDE convertor, into cramped compartment for 2.5 drive.
SATA->IDE convertors I have seen are designed for "external" connection where they get power from Molex (HDD or FDD) connector, and pass it to SATA side. If you can sacrify "mobility", you can still fit the adapter inside the drive cage, and use short cables to hang the SATA drive outside.
One think yoy may do is to look for adapter where you can put your hard drive into CD/DVD tray (I have seen some instructables about how to do it).
But - probably it's time for the old boy to retire. I have an eleven-years old Dell Latitude still working, and I haven't pulled it out of its leather case for years...