hard drive data recovery

I have a 160 gig SATA Maxtor hard drive provided by Dell. It is a secondary hard drive and contains data only. It seems to have started going bad. Several files are inaccessible. I have Windows XP Pro and ran chkdsk /r on the bad drive. It freezes at 51% on the third level (I think). I have looked at the long list of drive and data recovery software available on this site. I have tried a few (Zero Assumption, PC Inspector File Recovery, Unstoppable copier). Now I'm looking for advice and/or opinions on any particular software. The files are critical and need to be recovered. I'd say about 5 to 15% of the hard drive is bad or going bad. The computer itself is a Dell Dimension 4700.

PC Inspector File Recovery and Unstoppable Copier were worthless for my purposes. The free version Zero Assumption worked okay. It let me recover two folders. But I just wanted some advice before I spend money.

Thanks to anyone who can provide some words of wisdom.