my compaq presario cq42 says,windows have detected imminent hardisk failure *smart hardisk error 301* even after i formated the system it still says the error message on system startup.wat should i do?

Formatting your machine would not rid you of the message.

The hard disc has a self monitoring tool (SMART that actually has detected a possible physical fault with your drive. Now, this warning is "possible imminent" not "its going to crash today today", but then, there isn't a time line for the failure. I've had this same error on my laptop in the past, ignored and used it on, until i eventually changed the drive to a higher capacity one.

Best bet would be:
[list]
[li]- Back up your files[/li]
[li]- Get a replacement drive[/li]
[li]- Restore your data onto it[/li]
[/list]

And you may want to do this soonest.