F1 at Start Up

Hi, I recently had a power supply problem with my Dell Dimension 4700. 

As my desktop is well out of warranty I took it in to a local computer shop and while there asked if they could also update the memory to 2GB and install an additional hard drive.  Both of which they did as well as fixing the power suply problem and taking it upon themselves to fit me a new BIOS battery. 

Only problem now is when I start up the system I need to press F1 to boot the computer.  On pressing F1 everything boots up fine, using Windows XP OS.

Obviously I have complained to the shop but they just shrug and say it wasn't what they did and must be a problem with my existing hard drive. 

Before the problem with my power supply presented itself and I took the machine in for repair I wasn't having to press F1 to boot up and although this is not the end of the world, it is irritating especailly as it wasn't there before. 

I seem to recall that when my DELL was under warranty the computer has experienced a hard drive problem and the drive was replaced under the collect, repair and redelivery service that DELL operate. 

I was wondering if this change in hard drive may be causing the problem as when the BIOS battery was removed and the BIOS went back to it's original factory settings that it is now trying to find a hard drive that has been replaced.

Does any body have any ideas what the problem might be caused by.  You may have guessed I'm not particularly 'techie'

Thanks in advance