Hard Drive in fat PS2 goes slow after 2 weeks of use

The hard drive was used for 7 years in a computer. It was never very slow, but when i put in a ps2. I was transferring file at a pretty slow speed from a usb. I know using a USB is slow. 2 Weeks later i was transferring files again from a usb half way through it had a large drop from one speed to 700Kbytes/sec.
Another problem while transferring files from usb it freezes half way through.
I formatted it in winhiip and it is a 1TB HDD.