is a special card that allows you to flash RUU files with a different CID to your own device. IF you own a T-Mobile device you can flash it with generic rom.
The following instruction is credited to Paul of Android.ModacoRequirements:
ABD - part of the SDK, download SDK here
Windows PC - to run the SDK
HEX Editor - Download here
How to Create GoldCard - Step by step instructions
- Format the microSD card to FAT32 format.
- Put the microSD card in your device and boot it.
- Ensure you have unzipped the SDK, then open a command prompt to the extract location. Change to the 'tools directory.
- Enter 'adb shell cat /sys/class/mmc_host/mmc1/mmc1:*/cid' and press enter. You should get a very long number which looks like this: 532600bd227d9c0347329407514d5402.
- Visit this page, paste in your number and reverse it. In our example the result would be 00544d5107943247039c7d22bd002653.
- Visit this page, enter your reversed number and create your goldcard image, which will be e-mailed to you.
- Open the HxD hex editor. If you are using Windows Vista or Windows 7, you must run the application as administrator.
- Go to the 'Extra' menu and select 'Open Disk'. Under physical disk, select Removable Disk (your microSD card), uncheck 'Open as Readonly' and click OK. Note that you should select physical disk NOT the logical disk. This is important!
- Go to the 'Extra' menu again and select 'Open Disk Image'. Open the goldcard image that you received by email.
- You should now have two tabs - one is your removable disk, the other is your goldcard image. Press OK when prompted for 'Sector Size' (selecting 512 (Hard disks/Floppy disks)) and click OK.
- Click on the goldcard image tab. Go to the 'Edit' menu, choose 'Select All' then select the 'Edit' menu again and select 'Copy'.
- Click on the 'Removable Disk' tab. Highlight offset (line) 00000000 to offset (line) 00000170 (including the 00000170 line), then click on the 'Edit' menu and select 'Paste Write'.
- Click on the 'File' menu and select 'Save', accepting the warning.