Please load the BIOS Defaults and you can install Windows 7 on your Inspiron 1545. To load the BIOS Defaults:
1. Restart or Power on the computer.
2. As soon as the Dell Logo appears start tapping the F2 key repeatedly.
3. If the BIOS screen doesn't appear repeat steps 1 and 2 again.
4. Click the "Load Defaults" button at the bottom of the screen.
5. Click "Apply".
6. Click "Exit" to boot to Windows.
7. Now you can install Windows 7 on your computer, the Hard Drive settings have been changed to its original factory state.
Do reply with results.
To know more about Dell's products, services and drivers & downloads, please go to http://dell.to/YBlak6