Depending on how geeky you are, you might find it worthwhile to build yourself your own
BartPE disk - its little short of amazing what you can do with BartPE if you know how, and its free if you build your own. This would be my first choice; while it might or might not get the job done, it costs nothing but time and the price of a blank disk to try and will not affect the data on the subject drive unless you decide to do something to or with that data - without instructions (and perhaps additional software, depending on what you want to do) otherwise it merely makes data available. If you can see the data you want to recover, fine; go ahead and recover it however you care to. If it can't see the data you're after, just move on to plan "B", dedicated data recovery software. There's lots of it out there; do some research, read reviews, and look over the vendors' websites for particulars - look for FAQs and user forums.
I strongly suggest you make sure you're comfortable that the app you choose offers a fair chance of accomplishing what it is you wish to accomplish; whether you get your data back or not, once you've spent your money, there's damned little likelyhood of getting your money back.
I'll offer personal impressions of a couple data recovery apps. Bear in mind, I'm not recommending either of these, I'm simply saying what I think of them.
If the data is still on the drive and the drive can be accessed, GRC's
Spinright ($90.00, no trial version) likely will enable recovery of that data; it can take anywhere from hours to days to do so, depending on circumstances, drive condition and size, and the amount of data to be recovered, but its proven, over years of development and use, to be reliable, effective, and thorough.
Another well regarded app you might wish to consider is GetData's
Recover My Files ($70.00, trial version permits examination of subject drive to determine probability of recovery, registration and paid activation required to actually recover data). Again, depending on circumstances, it can take quite a long while to retrieve and transfer data, particularly if the drive is large and/or there's a lot of data to recover.
Whatever you use, you should have available an independent drive onto which to recover the data; an optical or flash drive may serve adequately, but I've found it best to use an actual hard drive, whether another hard drive on the subject machine, an external hard drive, or a hard drive on a machine networked to the subject machine.
I've used 'em, and have found they pretty much do what they say they'll do - if you're patient, and if you fully understand and carefully follow their instructions for use. If none of these do it for you, about your only other option is very pricey professional in-lab data recovery.
Prolly oughtta mention you should neither write to nor try to access the subject drive prior to initiating data recovery; overwriting will complicate things a lot.
Good luck.