I have noticed how many people are assholes to noobs when it comes to block ID conflicts talking about how easy it is to fix it.
Now, the first time I ran into a block ID conflict, I ran into the same situation where they thought I was an idiot. Fortunately, they told me how to fix it anyway.
So to prevent the people from yelling at the noobs and to prevent the noobs from being yelled at, I decided to make a thread about how to identify block IDs in crash reports and how to fix them.
1: If you scroll down on the crash report, you will eventually see the error, which is usually identified as null pointer exception, illegal argument exception, etc. So if it's a block ID conflict, then it will say block ID X is already occupied by Block A (not literally, X and A were used as variables)
Identify which block it is conflicting with and which mod it is coming from. So for example, I had an block ID conflict with gregtech and computercraft, and it said that a gregtech block was trying to occpuy a slot that was already occupied by a computercraft turtle.
2: Go to %appdata%, then roaming, then .minecraft, then config.
3: Find the mods that are conflicting with each other, in the example shown above, it's gregtech and computercraft. Open one of the configs which is conflicting using notepad (so in this case, I can choose to open the gregtech or computercraft config)
4: Find the block ID section. You can use the ctrl F function to find it.
5: change the block ID of the block that is conflicting. By that I mean change the number to something else. Make sure the number is 4095 or less, and ideally, since I think vanilla blocks occupied these slots, 257 or more. That time, I changed the block ID for computers and turtles in computercraft from ~4000 to 500-504 respectively. It is usually a good idea to change the block ID for ALL the blocks in the mod just to be safe.
6: CLose everything, making sure you saved what you did in the config. If the block ID is left blank, it will go back to the default so make sure you actualy inputted a new block Id for the block.
7: If you successfully changed the block ID and the new block ID for the block IDs you changed aren't occupied already, then minecraft will successfully load. If you did change it but got a similar crash report, try changing to a different block ID. If you didn't change it, then GO BACK AND CHANGE THE DAMN THING.
This thread should be helpful for noobs and experts, and I hope people take the time to read this so that there are less crash reports about ID conflicts and yelling.