I MAKE movies on my mac. I use a 1.5TB Seagate external hard drive to store all the footage that I shoot. Long story short, my mac isn't LETTING me open it without formatting the drive. Is there any way to recover my highly important files inside it?

Long version:
Today I needed to get some files onto my PC, so I plugged in the hard drive. My PC recognized that a drive had been inserted, but would not show it in the explorer. I did some searching and found that I could assign the drive a letter in the Disk Management section of the Computer Management tool. So I did it. My PC then proceeded to tell me that I could not open the driver without formatting it. So, I ejected it and plugged it back into my mac. Now, my mac told me the same thing. I now have an external hard drive that contains all of my filmmaking projects and cannot be read by a mac or PC.

Someone, please help! There must be a way to get this lost data back!

Specs:
Mac OS: OS 10.4.11
PC OS: Vista (Service Pack 1)
Hard Drive: 1.5TB Seagate Desktop External Drive
Hard Drive Format: Mac OS Extended (Journaled)

Thank you for ANY help or INSIGHT you may be able to provide.

EDIT: The only help that I have gotten so far on this issue is that the problem is the boot sector of the drive is corrupted. Is there a way to REPAIR the boot sector of the drive?

EDIT 2: Using the Disk Utility, I tried verifying the disk and this is what I got: Code: [Select]Verifying volume “disk2s1”
** /dev/disk2s1
Invalid BS_jmpBoot in boot block: 000000
Error: The underlying task reported failure on exit


1 non HFS volume checked
Volume needs repair