I am going to try. I might break this into multiple replies and might not get them all up tonight. I will assume you are in Windows 7 for all of this! I did use an Ubuntu Live CD to do the s-off procedure, but I think there is revolutionary instructions for Windows.
(1) First enable USB debugging on your phone by going to Settings->Applications->Development. Then turn off fastboot by going to Settings->Power (this is different than the fastboot mode choice once in recovery, which is used with the fastboot.exe that is part of the Android SDK.)
(2) Next install the HTC USB Driver for the Droid Incredible 2. You can find the download link in the XDA downgrade thread at [Tool] Downgrade VivoW with hboot 0.98 - xda-developers
(3) Install the Android SDK, which will include ADB and Fastboot. You can find the instructions and the download link here: What Is ADB And How To Install It With Android SDK
You can skip the USB driver install because you have what you need from Step (2). Fastboot is in the platform tools folder. I just moved adb.exe and adbwinapi.dll from the tools folder to the platform tools folder so they are in the same location as fastboot. I also place any files I am flashing to the phone, etc in that same folder. It just makes is easier to change to that folder at the command prompt and execute commands from there. (The easy way to open the folder at the command prompt in Windows 7 is to hold down shift and right click the folder. You will get a command window option.)
At this point you should have a C:\android-sdk-windows folder and the necessary files under it. If you have trouble to here, I don't think you should go any further.
As an alternative to step (3), and easier, is to download attn1's kit from [Tool] Downgrade VivoW with hboot 0.98 - xda-developers
. It contains the files necessary to run adb and fastboot without installing the Android SDK. The key is to put all of the files from his kit under .\tools\win in the same folder as the files in the root folder of his kit (namely misc_version, zergRush, etc). Put them in c:\adb would be my suggestion.
Assuming you did the paragraph above, which I recommend. Do the following:
(4) Open the command prompt and change to c:\adb. Connect your phone via USB as charge only. You should have USB debugging enabled per the above. Manually execute the commands from attn1's downgrade thread. Namely:
adb shell rm -r /data/local/tmp/*
adb push zergRush /data/local/tmp/zergRush
adb push misc_version /data/local/tmp/misc_version
adb shell chmod 777 /data/local/tmp/zergRush
adb shell chmod 777 /data/local/tmp/misc_version
adb shell /data/local/tmp/zergRush
adb shell /data/local/tmp/sh -c '/data/local/tmp/misc_version -s 2.18.605.3'
adb reboot bootloader
fastboot oem rebootRUU
fastboot erase cache
fastboot flash zip RUU_Vivo_W_Gingerbread_S_VERIZON_WWE_2.18.605.3_Radio_1.09.01.0622_NV_VZW1.92_release_199487_signed.zip
At this point, you should have downgraded your hboot and can gain s-off.
(5) Attn1's thread also contains the link to gaining s-off and installing cwm (clockworkmod recovery) using Revolutionary: Revolutionary
You should be able to run this per the instructions there. This will set security off and install the clockwordmod recovery. You can follow this thread for more thorough instructions: [How to] Root Your DInc2 Tutorial! (2.3.3 GB Only) - xda-developers
At this point you are downgraded with s-off and clockworkdmod installed. You now have everything you need to flash ROM's, etc.
(6) You should read about flashing ROM's, etc here: Ox's noob corner (work in progress)- everything you need to get started right here - xda-developers
There are other resources if you search.
(7) You get into recovery by turning off your phone. Then hold volume down and power on. Then you use the volume keys to move the cursor up and down one in the bootloader. Use the power button to choose options. The same goes for once you are in recovery. You should see an option called "recovery" once booted into the bootloader. This will run CWM. The first thing you should do is do a nandroid backup in the backup and recovery menu. Make sure you have a least 1 GB free on your SD-card (I keep 4 GB for experimenting with ROM's). This will backup your stock ROM setup.
(8) Now you can reboot, download ROM's to your SD card and flash them as instructed. Good luck.