RAM is made to industry standards.
Laptops use SO-DIMMs Desktops use DIMMs you will find three versions in common usage for both form factors, DDR, DDR2 and DDR3. Additionally these parts are made at different clock frequencies ranging from 400mhz to 1600+mhz. The mini 9 interfaces with its DDR2 memory at 533mhz. Regardless of the speed of the memory the Mini 9 can only talk to it at 533mhz. Some computers can talk to RAM of the correct type that is slower than spec, while others cannot. Your best bet is to match whatever speed you have originally. Each type (DDR, DDR2 and DDR3) must be matched to its proper socket, they are not interchangeable.
Short of it, Mini uses DDR2 SO-DIMMs, and nothing else will fit. You can use 667mhz or even 800mhz DDR2 in it but the mini will only use the ram at 533mhz. The 1525 has multiple processor options, some of which can make use of 800mhz DDR2, so if they work with the slower mini 9 RAM you would experience diminished performance.
tl;dr You need to tell us more, and if you could use better grammar that would be nice.
Netbooks -> Mini 9 - 2gb Gskill low latency - Ubuntu 8.04
Asus Eee 701 4g - 1gb - Ubuntu 8.04.1
Desktops -> Phenom Quad @ 2.8 - 16gb - 4x Raptor X in RAID 0 - 2x 4870X2
Brisbane 1.9 @ 2.7 - 4gb - 80gb
Many others, all Linux.