Dismounting the cover needed a strong power. My cover was damaged by the movement of the scraper. But, these damages has been on the bottom of mac mini. Nobody might not sorrow brush burns on the bottom. Then, I had finished dismounting the cover:
You can see the default memory module at the right side of the picture. The silver plate is over the memory module:
I could yank the plate easily. Then, I replaced the default memory module with 1GB memory module which I bought. In that process, I broke some plastic parts. Be careful.
I inserted the silver plate to where it was before. Then, I mounted the cover and kick on mac mini. Mac mini could be waked up without any troubles. So I became able to use mac without memory swapping. The 512MB memory module which I removed from mac, will be used to other windows machine.
My 1GB memory module is PC3200 CL3, which is bulk goods and about 11,000 JPY. I want to recommend the memory exchange to Ryuji, who is a mac mini owner also. But, His mac seems to be iTune only.
In fact, you can watch the tutorial video here.