Wont read my external harddrive

I have a seagate 500GB external hard drive that I have used on my old HP, I recently bought a brand new mac book pro, I have looked through a lot of forums to get an answer and have tried pretty much everything that people are saying. I have gone to my utilities and it shows up there but I can't do anything with it besides erase it. I don't want to erase it cause there is a lot of stuff I want off of it. I have gone to my preferences and checked all the boxes like everyone else said but nothing works. it still reads on PC's but it won't read on my MAC. I know the cable works cause it works on my seagate 1TB and it reads fine and I have tried rebooting my computer and there is no sercuity setting on the hard drive. Please some one help me, this is getting really frustrating.

Welcome to the Mac Forums.

The Seagate is very likely formatted to NTFS which means your Mac can see the files but can not make any changes. The entire drive is read only and may not even allow copying the files because of ownership.

What you can do is install a driver on your Mac which will allow reading and writing of the drive from OS X. The best driver is $19.95 from Paragon Software. Here is the LINK to download and purchase.

If you are using Lion check this link

https://discussions.apple.com/thread/3191198?start=0&tstart=0