What X15 coin are you trying to mine? Reason I ask is because there simply aren't many of them out there.
The answer to your question on how to mine X15 with a CPU on Windows 7:
(This is for a stratum pool, not solo mining. This will also work on Windows 8, and Vista.)
1) Download the X15 CPU Miner:
https://www.dropbox.com/s/hnleulsps90opt9/miner.rar
2) Unpack the files to a new empty folder, then create a new text document (right click > New > Text Document) and open it.
3) Copy/paste the following command into the document:
minder-corei7.exe -a bitblock -o stratum+tcp://STRATUM_URL:PORT -u USERNAME.WORKER -p PASSWORD
4) Replace STRATUM_URL and PORT with the info provided on the pool's "Getting Started" page.
5) Replace USERNAME.WORKER and PASSWORD with yours from the pool's "My Account > My Workers" page.
6) Finally, save the document as something like X15_pool_1.bat (<-- notice: .bat NOT .txt)
7) Double-click your newly saved X15_pool_1.bat file and it will start the miner.
I get around 91 Kh/s with my i5-2500K.
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