Auto rebooting after xx hours.

Hello people,

Hope some people can help me,this is a strange one.I’m running winXP pro on broadband (BTopenworld),using Acatel speedtouch USB drivers v1.4.3.After some 4 hours,the computer automatically reboots.However,if I upgrade the Acatel modem drivers/software its okay,but the computer runs slow.

Anyone know what this could be?

Many Thanks.