My iphone 4 is very slow.....

I've tried a hard reset but didn't help. ???

Sounds like a restore is in order next.

Check out the new remodeled MacOSG website! 24-hour Apple-related news & support.
 MacOSG: An Apple User Group  iTunes: MacOSG Podcast  Follow us on Twitter: MacOSG

Hi,

If you've already tried a Reboot and a Reset… Then the next thing to try is a Restore...

See this Link for Restoring:

http://support.apple.com/kb/HT1414

Hope this helps,

Cheers

Did you try restore? Also, if you double click home button after the hard reset, how many apps do you see? If you see all the various apps try to press and hold and close all of them, then reset the iPhone again.

I had the same problem but powering the phone off and leaving it off for 5 minutes solved the problem.