Ps3 – How to fix correct hard drive not found error on PS3

From How to upgrade your PS3 internal hard drive:

Things you will need

1. Larger SATA notebook (2.5″) hard drive (hd), 5400rpm or 7400rpm.

So unfortunately with your 3.5" hard drives you are out of luck - they won't fit into the PS3 and they are the wrong type (ATA vs. SATA).

However, all is not lost. From the same site there's a post on How to add an External USB hard drive to the PS3

If you have amassed plenty of videos, music and pictures on your computer over the years then why not stick it all on an external hard drive and hook it up to your PS3. Easier, and much quicker, than streaming files over your home network this is an ideal solution for users with massive hard drive needs.

With the advances in the PS3 software, many video types can now be played and nearly all music and picture formats are also available.

So if get hold of a 3.5" enclosure with a USB interface you should be able to use the drives like this.

It really depends on your usage. Many PS3 games have a forced "install" where sometimes multiple gigabytes of data are copied to HD storage for fast in-game reads (looking at you Metal Gear Solid 4). As well, some games on PSN can be quite large, not to mention that PSN has a few full-fledged retail PS3 games available for download, as well as high def movies.

Having said all that, it looks like Rock Band song downloads are around thirty megabytes a piece, giving you space for ~500 songs on the 120gb model.

Also, the commenter above is correct, the PS3 (including the slim) can be upgraded with any 2.5 inch HD in the future if you run out of space.