Hi Guys, I'm new to iMAC. I've got an external hard drive that contains 800gb + data and used it with PC before. So now when i attach the drive to iMAC it says "Cannot Read this file System" What should i do? and should i make it work?

what OS has the other computer you used the hdd on ? maybe Imac doesn`t support that file system ( MOST LIKELY ) our patience is big

Modern Intel Macs running Mac OS X 10.5+ can read NTFS, FAT32 and HFS(Mac native file system). If you are going to be moving data back and forth use FAT32. Windows PCs will not 'see' HFS as a valid FS and would ask to format it to NTFS or FAT32.

@imperator .. as i said above i used that HDD on WINDOWS XP. I got data there and i need to use it on mac, how should i access it and what should i do.

download linux live cd and then you`ll be able to access your data maybe iMac can`t read your current file system our patience is big

LINUX LIVE CD? where wud i get it? and what it is for? provide a brief demonstration.

that is a disk operating system you can backup your data to another partition or hdd once you backup your data to another partition, you can delete the partition that you backuped your data from then format it using mac ( mac will format it with a format that supports and then you can to restore your data ) you can get it from here burn the iso with an image burning software ( you can choose one ) and boot from it then backup your data somebody correct me if i am wrong sorry for the delay our patience is big