Physical dump of memory problem HELP?

i have an advent (not sure about model) and it used to work absoloutly fine until one day, when it turned on as normal, but then it came up with the screen where it says do you want to start windows normally (etc) and i clicked on start normal. It takes me back to the screen where its says about starting windows normally and i have tried every single one on the list bu they all do the same thing. How can i sort this! HELP