WD Sata Harddrive won't boot....... toast ?

I have a 500gb Western Digital Sata drive.....drive has two partitions, one with windows XP.

Yesterday I started having problems which escalated quickly......first explorer was crashing regularly trying to open video files. Then, upon rebooting, I got the "disk read error" msg.

So I re-installed windows xp on another drive, booted up, and was suprised and delighted to see my sata drive contained all the data and partitions, which were 100% intact...... only problem was it would only boot up in PIO mode. After trying different suggestions online, and rebooting..... the disk stopped showing up in XP altogether. Even in the disk management section.

Since then, for the most part, it'll show up in the BIOS 99% of the time......but upon booting windows xp, it'll either hang completely...... or take an excessive time to boot up at the winXP logo screen, and then not show up anywhere in windows.

There's about 400gigs of video that's real sentimental and important to me, so I'm just wondering if there's any way to recover it, or am I screwed? I am considering at least getting a quote from a professional data recovery center.... but I hear they can be pricey, and easily get into four figures. Is there any easier and less costly way to go about it? Or by the sounds of it, is the drive too physically damaged to go through with any software route? I'm reluctant to keep booting the drive up, as I'm scared I'm damaging it further...