Recenlty bought a USB Stick, when i boot up the pc, it says "invalid disk system", so i have to remove the stick for the pc to load. Kinda strange, any suggestions?
Sounds like your PC is trying to boot from the USB stick rather than your hard drive - to stop this go into your Bios boot menu and select your primary hard drive as the first boot device.
Out of interest why do you need to boot up your PC with the USB stick connected anyway?