Could not find any compatible direct3d devices

Hi

Is your PC a Dell http://www.dell.com/support/drivers/us/en/19/Product/dimension-1100

If so then where the games that do not work now the same as you had working previously? if so what where the games?

Did you do any driver updates recently?

I'd say best course of action is to re-install your chipset and reboot and then the graphics driver (if the graphic card in your PC is the original one it came with, if different then please advise as to make and model)

Chipset Driver
Graphics Driver

Reboot after each and test the online games or screensavers once the graphics driver is installed,

Its very possible that if the games or screensavers are different to the ones that worked in the past that your graphics card is not powerful enough to take advantage of those softwares.