Toshiba T9100 Laptop Help needed

Toshiba T9100 laptop, just started having this problem, when I switch on it will not boot until I press the switch several times, then as soon as windows starts to load it shuts down completely, I have tried changing the battery and power lead but still does the same, can anyone help? Operating system Windows XP

Bad PSU perhaps.

does it make any beeps?

whats PSU mean? no does not make any beeps just closes down

the PSU is your Power Supply Unit.

is the computer getting really hot?
have you tryed safe mode?
can you get anytime useing windows?(how long after it starts will it turn off)

it may due to the memery effect,when you first using the batery,you should discharge the battery 100%, and than charge it 100% full.Although you may haven't done this,you can now discharge the battery completely empty,and charge it over full,just more 3-4 hours charging.if it still don't work better,change a new toshiba laptop battery.on the other side ,your adapter should work in the conditon of no battery, if it often shut down suddenly, check the AV/DV voltage convertor,if it is decline,u'd better change the adapter,here is some links
http://www.toshiba-laptop-battery.comtoshiba laptop battery
http://www.toshiba-laptop-battery.com/ac-adapter.htmtoshiba laptop ac adapter
http://www.toshiba-laptop-battery.com/80w-dc-adapter.htmtoshiba laptop dc adapter