I bought new HDD and I was told that it had 100mb/s speed but when I copied some music files from one partition to the other and calculated the speed it came around something like 10mb/s, why is this big difference present ??I was shocked to see this.

Thats peak speed on the bus, a normal hard disk would never reach that speed in real life (physical limitation). Thats why a SATA300 drive doesnt have 3x the performance of an ATA100 drive, they are very similar in performance due to the limitiation of the disk spinning etc.

The 100MB/SEC is the max speed of the IDE interface.

You would need 2 or 3 drives in a RAID-0 stripe to reach 100MB/SEC.

The new SATA standard is 3.0Gb/sec (which is about 380MB/SEC) really means nothing unless you have an array of like 6 disks in an enterprise setup linked.

The maximum burst speed of the ATA100 interface is 100MB/s, but the transfer rate from the disk platters is much lower. This is why a larger HDD cache is better - it'll be able to sustain longer burst transfers.

10MB/s is quite a normal speed, do not be concerned about it.

Thanx everyone for the info.