BIOS update on Dell Optiplex fails; disk i/o error. I tried a floppy; I'm local admin. What's the dilly-o?

Hello,
    I have 2 GX270s (WinXP, SP3), and noticed that they're on A03; so, I went to support.dell.com and searched: http://search.dell.com/results.aspx?s=gen&c=us&l=en&cs=&k=gx270+bios+update&cat=sup&x=0&y=0 and downloaded the A07 update. On GX270 #1, it shut everything down, it rebooted, everything worked; that system is now at A07. On GX270 #2, I can execute the file (Running the executable displays a screen that acknowledges my current BIOS level, tells me if it has a valid update, and asks me if I want to apply it), but when I hit 'Continue', I get this message:

Dell System GX270 BIOS Flash A07: An error was encountered accessing the local system drives, please reboot and try again. If this error re-occurs, please contact technical help.

I rebooted as advised. I re-downloaded the update to make sure the file wasn't corrupted in transmission. I even copied over the file that worked on GX270 #1. After that failed, I remotely accessed the file that worked earlier by opening a window to \\GX270#1 (not its real name). I copied the file to a floppy; same thing. Maybe you're thinking it's permissions. I'm local administrator. Thinking further, I turned off DEP for just that file, and did the reboot necessary to test that. I checked the file's properties to make sure that executing the file wasn't prevented just because it came from without. Hence, I turn to you. Thanks.