Windows 7: Seagate external hard drive not recognised by my computer

I have attached a Seagate 500 GG external hard drive to my computer but it is not showing up in My Computer. I have browsed similar threads and on their advice gone into Device Manager. The drive is there but with no letter assigned to it but when I right click to assign one, it refers me to Windows Help, which is unable to solve the problem. There are actually two extra ikons in Device Manager - one marked FAT Healthy (EISA Configuration) and the other just marked (GPT Protective Partition). The device is acknowledged as working properly in Device Manager
The files on this drive were created on a Mac, which may be the source of the problem? Most of them I will therefore not be able to read, but there is one which is a .mov file which I should be able to read and hopefully copy - if I can access it.
Is there any way I can access the drive via my PC (Windows XP) or will the drive have been formatted for Mac only and therefore is inaccessible via PC?
I'm afraid that's the best I can manage in terms of technical information. Any advice would be much appreciated please.

I would venture a guess that the simple answer is that the drive was formatted for a Mac and windows is unable to recognize it as such. Now, being said that, with the newer technologies and emulators that Macs and PCs use, I am not 100% sure.

Now for the dumb question, have you tried plugging it back onto the Mac and see if you can read it and copy the file and then format it to the pc so you can use it? that is, if you will need it more on the PC than on the Mac.

Many thanks for your advice Asta La Vista.
Haven't yet plugged drive back into the Mac but it was working ok yesterday so that shouldn't be a problem. As the file is in .mov format it is already readable by the PC if I can access it. The problem is I can't open the hard drive in the PC. And the file is too big (6+GB) to go onto a memory stick. Even if I deleted all the files except for the .mov one that are on the Seagate, sounds like I still wouldn't be able to open it if the drive is Mac formatted - does that make sense? Other files readable by both systems I have transferred from one to the other using memory sticks.
I do need it on my PC as it's the final version of a film I've made and the screen and speakers on my PC are vastly better than those on the MAC notebook
How I wish these systems would talk to each other!

it makes perfect sense but it also makes sense, at least in my head, that since the whole drive was formatted for the Mac, that a PC computer would not be able to read the whole drive.

Now, I take it that the thumb stick has the capacity to hold the .mov file but because the restrictions of only allowing 4GBs you can't move it?

If so, have you tried splitting the file? HJSplit would help and then, after you have save that file you can connect the drive on the pc and format it again so it works for windows.

I am having similar problems with my 2TB goflex, my laptop just doesn't want to assign a letter to it but, I don't want to highjack your thread and I have already posted my problem on another thread.