From the software's author:

Pinball Browser currently supports the following firmwares :
- Stern/Sam firmwares : fully supported ;
- Stern/Spike firmwares : fully supported, except for the communication patch that is not available; At prensent time, videos cannot be imported in some games.
- Stern/Whitestar : Atmel and 6809 boards; Pinball Browser can only play and modify sounds;
- WPC games : Pinball Browser can only display DMD frames. No other features are supported. No modifications are possible.

How do I open a Spike firmware ?
There are 2 options :

1 - The prefered method : Open an image (.img) of the game SD card :
* For Pinball Browser v6 :
Just insert the game SD-card into your PC and use the "Read image from X:"; Pinball Browser will make an image of your SD card and save it on your hard disk.
Modify what you want in this image. Once it's done, the modified image must be written to a SD-card, not a thumbdrive.
Do not use the original SD-card (keep it as a backup); use a new SD-card; no need to format it.
Use the "Write to SD" function in the SmartDmd tab.
* For Pinball Browser v5 :
Use Win32DiskImager to make an image (.img) of your SD card
Open the .img file with Pinball Browser and modify what you want
Use Win32DiskImager again to transfer your modified image to the SD card (it is strongly advised to use a spare SD card and keep the original one unmodified)

2 - Open an .spk or .000 file (available on Stern's website) ;
The main drawback of using a .spk file (compared to a .img) is that you'll only see what's included in the upgrade package (for example, if some video files are not modified with the upgrade, you won't see them in Pinball Browser).
If you open a .000 firmware, Pinball Browser will convert it to a .spk file. This .spk file cannot be used to upgrade the game (because it's bigger than 4Gb and cannot be copied on a FAT formatted USB stick). You have to convert it back again to .000/.001 files before upgrading your game (click on the button next to the Open button and select 'Pack firmware for USB stick').