Driver_irql_not_less_or_equal + Bad_pool_header

Can anyone diagnose the cause of this message?
The computer keeps restarting all the time, yesterday I had this message 6 or7 times
But apparently it is only when I go on internet. For example, I dial up, and if I am lucky I get to the page I want, before the computer die, for instance Techspot, but if I disconnect the computer can stay turned on for ages, odd.

Driver_irql_not_less_or_equal
Stop: 0x000000d1 ( 0xf997b45b, 0x00000002, 0x00000000, 0xf41a29ed )
Mtlstrm.sys – address f41a29ed base at f40da000 datestamp 3e4faf50

Driver_irql_not_less_or_equal
Stop: 0x000000d1 ( 0x8c8a547e, 0x00000002, 0x00000000, 0xf3fbb41f )
Mtlstrm.sys – address f3fbb41f base at f3ef2000, datestamp 3e4faf50

Driver_irql_not_less_or_equal
Stop: 0x000000d1 ( 0x7a9c3a87, 0x00000002, 0x00000000, 0xf49e5a1d )
Mtlstrm.sys – address f49e5a1d base at f491d000, datestamp 3e4faf50

Bad_pool_header
Stop: 0x00000019 ( 0x00000020, 0x81e87f38, 0x81e87f68, 0x0a060010

Go here (http://www.aumha.org/win5/kbestop.htm) for an explanation of Windows error messages.

The Mtlstrm.sys is one of your modem drivers try getting the latest drivers and or uninstalling and then reinstalling the drivers.

Regards Howard :grinthumb