I had actually compiled it a couple of weeks ago, but I never could get it to work. I was looking into it again tonight and discovered that windows had installed the USB Mass Storage driver for the phone in SPL mode, instead of the android driver. So after updating it to the android driver, it worked! woot
(note: you have to check the USB device in Computer Manager when the phone is in fastboot mode. The computer sees the phone in fastboot mode as a different device than the phone in normal mode)
Download the file and extract it in the same folder as adb. (if you don't have adb yet, it's included in the android SDK for windows. go download it!)
Take out the usb cable and boot up your phone into the SPL (back + power). You have to have the dev bootloader for this to work (white background with 3 skateboarding androids).
Plug in the usb cable, and make sure the display on the phone changes from "Serial0" to "FASTBOOT". If it doesn't, try pressing the back button.
If it asks you to install drivers, then go ahead and use the same usb drivers that you used to get adb working. You can skip the rest of the instructions. Fastboot should be working for you now.
If it doesn't ask you to install a driver, you need to figure out if the correct driver is loaded already.
Right click on My Computer, and click Manage, then go to the device manager
If you see an "ADB Interface" category at/near the top, with "HTC Dream" under it, then you're good to go. Fastboot should be working for you.
If you don't see an "ADB Interface" category, then it's likely that windows loaded the USB Mass Storage driver for it automatically. In the device manager, go down to "Universal Serial Bus Controllers", and see if you have at least one "USB Mass Storage device". If you have multiple ones, you'll need to go through each to find the correct one.
To find the correct one, right click on the USB Mass Storage device and click Properties. Go to the Details tab. In the combo box at the top that says "Device Instance Id", bring up the pull down and choose "Compatible Ids". If that is the correct device, then you will see 3 entries:
Once you find the correct device, go to the driver tab, and click "Update Driver". Choose "No, not this time", then "Install from a list or specific location", then "Don't search, I will choose the driver to install", and then choose the same usb driver that you used to get adb to work.
After that's done, you should be good to go. Open a command prompt and type fastboot devices and it should list the phone.