Although I do agree with the above, there is a way around it.
But it will require a reinstall of your OS anyway.
You could partition up the drive into 2 parts: the first 100GB, and then all the rest.
Don't allocate, format,or activate the first partition, leave it "blank" or "RAW."
Then install your OS to the second partition. Your system will be a little slower, as it's not reading the first 100GB of the drive, which are typically the faster, but it'll work.
If this is something you'd like to try, let me know. I can draw up how to do it during a Windows install.
I don't think shrinking the volume in Disk Management will work, as you will need to move the first 100GB, not the last.