So, I finally figured it out. The SSD shipped already partitioned and formatted from Dell on this system. I deleted the partition and ran the Intel Rapid Stor software again and now it gives me the option the accelerate the hard drive using the SSD.  Really disappointed that this computer shipped with the SSD partitioned and formatted, making the acceleration feature unavailable until the partition was removed. Hopefully if anyone else runs into this issue they will find the answer here, rather than having to keep experimenting the way I was forced to do.
 I am having an issue with my XPS 8700. This is my second of this model, as the first failed and was replaced under warranty, but as I recall had the same issue. I am running Windows 10, but the system came with 8.1 installed. This version of the model has a 32GB SSD, as well as a 2.0 TB hard disk.  In the Intel Rapid Storage application the 32 GB SSD shows status as Available, but under the Performance tab I only see Link Power Management settings. I've dug through the help available from Intel and it appears that the SATA settings in the system's BIOS need to be set for RAID, which my system is not. I've tried changing the setting, but then Windows refuses to boot at all. I had to toggle the SATA setting back for Windows to boot again. So my question is, was my system never set up to take advantage of the SSD for caching? The BIOS setting are as they were from the factory, so it appears that the SSD feature was never implemented at all. If I read correctly I can switch SATA back to RAID but then I need to reinstall Windows to get the system to boot, which I would like to avoid, as I did it several dozen times with my first, failed system, and twice with this one, which takes forever as the Dell Backup and Recovery app takes me back to Windows 8.1. So, can I get this working without a reinstall of Windows? I would like to finally take advantage of the hardware I paid for.(I found a 3 year old post with the same question, but the responses were not particularly useful and when I posted this question to get additional info no one replied. Pardon the duplication, but a new question seemed to be the only was to get additional help.)
Disk acceleration via SSD not enabled on XPS 8700