Your problem may be solved with a software called
SpeedFan
You dont need to worry until and unless you start getting some boot errors, crashes, frequent hangups or clickin noises from your pc cabinet.
The slowness can occur due to several reasons.
Keep your registry clean.
Try not to use other programs while copying.
Check for spyware and other malware.
For faster speeds, disable your Antivirus program during copying.
And
Stay cool yourself. 8)
Savvy!