Your motherboard also has to support caching. Since you did not tell us the model # of it, we cannot answer your question.
Yes, Windows must be installed in RAID, not IDE or AHCI, to use RST / SRT. Conversions from IDE to RAID and AHCI to RAID are possible, but both the registry and BIOS will need to be modified. People have already asked this question on Microsoft forums. Go to Microsoft Answers and search for the proper registry settings. Search on "convert from IDE to RAID" or "convert from AHCI to RAID".
As we understand you would like to have your 25GB SSD for caching, that can be done using Intel® Rapid Storage Technology (Intel® RST) found here: Download Intel® Rapid Storage Technology (Intel® RST) RAID Driver, as well you can download the Intel® Smart Response Technology, in order to properly set it up, please read the following guide: Intel® Smart Response Technology User Guide.
Please let us know if you still require assistance.
From nestor_intel's second link, referring to the requirements to employ a cache SSD:
Intel Z68, Z87, Q87, H87, Z77, Q77, or H77 Express Chipset-based desktop board
Intel Core Processor in the LGA 1155 or LGA 1150 package
Operating system: Windows 8 or Windows 7 (32-bit and 64-bit editions)
This is why I noted that the motherboard (actually the chipset) is an important partner. Also, that document implies that no mobile systems can run it, as LGA 1155 and 1150 are desktop sockets. And Windows 10 is a non-starter.