first of all let me thank all you kind gentlemen for your responses, i'll try to elaborate.
when i first installed XP two days ago, after the initial installation it worked ok, giving me a thirty day period to activate the disc. i logged off and shut down the computer, when i later started up the computer i got a message saying,
"the date/time on your system is invalid. please use the date/time applet in the control panel to properly set your system time." i clicked ok which is the only option offered.
i then get the following,
"this copy of windows must be activated before you can log on"
if i reset the computer and go into settings and then standard CMOS settings the date displayed is 22 Oct 1999, if i change this to todays date and press F10 to quit and save then reload XP it works fine until i turn the computer off. and then restart it then the time reverts to 1999 and i.m back with the same problem.
hope this is of assistance. regards graham.