Just fell into some bad luck myself last night when I was flashing 5.0A onto my drive.. Floppy disk died on my through bank 3 (for the first time since I ever started backing up btw)... I panicked ofcourse since this was the first time that ever happened and thought I was SOL...
I started reading about the Bad Flash Recovery Method (or 10 Sec Method as some people call it) and read over DOZENS of differnt ways that people got their f'ed up drives working again... Well I'm just here to show (like eveyone else online) how exactly it was that I did it lol..
Only difference is that I'm pretty much writing it so that if I ever need to do this again (hopefully never cause I'm sticking with CD-RW for booting to DOS and never using Floppies again) (My comp can't boot to USB thats why I'm stuck using CD's btw) then I can just re-read the steps I used so I don't forget them later lol..
My drive was a MS25 (March 06) and it wasn't completely bricked, it just didn't eject or spin up... MTKFLASH still recognized it in DOS btw as well...
I have a VT6421 SATA PCI Card connected to my pc because my motherboard is the old school IDE-ATA (I know, I know)
Mind you I was up for like 8-12 hours reading through threads and trying different methods and failing each and every time before reading one last different approach (well slightly different because all methods are almost the same with just slight variations) and I was gonna try a few more times before I gave up and presto... Flashed
Well heres what I did...
1) Had the Xbox360 Samsung TS-H943 drive connected to my PC via SATA (Both the PC and the 360 were powered off)
2) Powered on the PC and let my floppy boot into DOS. When it did I typed MTKFLASH w /m /sata orig.bin (as I wanted to flash the original firmware and not any modified ones) but DIDN'T hit enter yet...
3) Powered on my 360 drive and let it boot to the Main Menu...
4) Pressed enter on my PC and MTKFLASH loaded up and showed me a Menu with all current selections including my VIA chipset...
5) Powered OFF Xbox 360... and waited ATLEAST 5 seconds after I turned off the system (This is cause right after you turn off you can still here the motor from the fan working.. just wait for that too turn off...)
6) Pressed button corresponding to my VIA chipset and got the usual error "Port: 10d8, Master/Slave: a0" (you will get the same or a slight variation of the same error...)
7) Started counting to 10 right after I pressed it...
(Now realize this people, its not a regular count to ten.. I tried many tens, fast, slow, clock ticks, stopwatch, and all didnt work.. I just after a while developed my own time speed for counting to ten.. Like I said, its not an exact 10 that you can time with a watch or stop watch as that DIDNT work for me.. But who knows it just might work for you! Mine was more like a 1,1,2,2,3,3 ect.. counting outloud kinda thing... You get the drift...)

After the 10 count, I turned on the Xbox 360 and the flashing started immediately...
Now this was the final method that I was using the last couple of times before it actually worked... If step 8 didn't work for me then I did the following...
(Extra Mini Sub Tuturial for when step 8 failed instead of flashed)
A - I would press escape so that the MTKFLASH would quit and I would be back at the DOS Prompt..
B - I would turn off my 360 (and wait 5 sec or more till the fan turned off)
C - Once the 360 turned off I would then type MTKFLASH w /m /sata orig.bin but DIDN'T hit enter yet (as I did in step 2)...
D - I would then power up my Xbox 360 till it got to the main menu, and pressed ENTER on the PC.. If the selections showed my VIA chipset then I would repeat steps 5 to 8 from above again...
E - If it didnt I would repeat the process from Step A (in this mini sub tuturial) until my VIA chipset showed in the list.. After it showed then I would repeat steps 5-8 from above (the main tuturial)...
Now remember this.. For some it might work right away.. For others it might take HOURS, DAYS, or even WEEKS... Some may NEVER do it.. There is not a GUARANTEED guide that will get yours to work.. There are MANY methods... Some might work for you, others might not... TRY ALL OF THEM.. Research and attempt all the methods!! The key to getting this to work is to HAVE PATIENCE and not to expect it to work right away... You will frustrate yourself.. You will want to give up.. But keep trying..