Lion Upgrade - now external HD wrong format

Hi there, recently upgraded my OS to Lion and everything seems to have worked smoothly except that one of my external HDs (a Western Digital 2tb My Book) is now showing formatted as "Windows NT Filesystem" and will not mount from disk utility. Verify Disk and Repair Disk do nothing. HD doesn't show in System Profiler.

Odd thing is that I have an identical HD which didn't change formats and works just fine.

Anyone have any suggestions on how to format, mount, and access the HD in question?

Thanks.

10.7.4
2.8 Ghz intel Core i7
16Gb memory

A hard drive can not arbitrarily change formats. How were you using the drive before you upgraded to Lion? Did you have an NTFS driver installed so that the drive could be read and written to? Snow Leopard had a built in capability to read and write to NTFS drives but that no longer works in Lion.

Thanks chscag. That must be what has happened, the drive had always been formatted this way and now I don't have the immediate capability to access it from the mac. Any suggestions on how I might be able to do so?

You could copy the data to another drive temporarily and reformat it as either Mac OS extended (Mac only) or FAT 32 (Mac and PC). The FAT 32 format is only useful if you are going to be using files that are less than 4 GB.

Perhaps a better alternative is Paragon NTFS for Mac OS X software. It is not free but will allow you to both read and write to NTFS drives from your Mac so there is no need to reformat.

Awesome, thanks slydude. I'll give Paragon a whirl.

You're welcome. There are a couple of pieces of free software that do the same thing but I can't attest to their reliability.

Yep, Paragon does the trick. Thanks again to all.