You could be more distro specific. And give us some more details on your proccess :
1. Create a USB boot disk with whatever distro you like
2. Boot your computer -> BIOS -> Boot Priority -> Select the USB device as first boot device
3. Reboot computer and follow the installation proccess.
4. You ll get to a point in which you need to partition your hard drives, this being the point in which you can either Install Linux allongside Windows thus getting a DualBoot option at startup, or erase everything and install Linux as a standalone OS
5. When the bootloader selection screen appears, chose Grub2 or Lilo ( depending on distro ) and set it to boot from MBR (Master Boot Reccord) thus giving you the posibility to boot Linux after restart without the USB plugged in.
6. After you chose whatever is that you need, continue following instruction until the install is finished.
7. Remove the USB and restart.
Hope this helps.