I have a netbook that is running a 2.5" HDD and want to go to a SSD drive, but most that I find that matches my capacity needs are Sata III drives are they backward compatibile to the Sata II interfacr that I have?
SATA 6Gb/s drives should be compatible with SATA 3Gb/s systems, granted they run at SATA 3Gb/s when not all relevant parts of the computer can support SATA 6Gb/s. Any modern SSD should run fine on your laptop without the SATA version doing anything more than cutting down on maximum performance. It won't make the drive less snappy, but it would hurt maximum transfer rates, granted these probably aren't very important for a laptop user (or even most desktop users) compared to the random access times that the SATA interface does not have any effect on.
For a laptop, I recommend a Samsung 830 SSD because they don't hurt battery power (they use almost zero power even at load) despite also being one of the fastest drives and having good prices. I think that they come in 64GB, 128GB, and 256GB capacities. Any other SSD would use exponentially more power despite often being either no faster or being slower. For a hard drive replacement, the 64GB capacity is probably best skipped for either 128GB or 256GB, depending on your budget. There might be a 512GB model, but if so that would probably cost upwards of $600 and is probably not what you're looking for.
Don't get the OCZ Agility 3. It has a known issue of dropping to SATA 1 speeds even if a SATA2 interface is detected (it's a SATA3 SSD).
Otherwise you should be fine.
FYI, I discovered that 60GB was not enough but for some people it might be.
Also, what you want to do is CLONE the hard drive to the SSD. You can investigate that but you might either have to put both drives in a PC to do it or put the SSD in a USB drive case and hook it up.
Or you could use the free version of Acronis True Image (if a Western Digital or Seagate drive is detected you can use the software from the appropriate WD or Seagate site). In this case, you could say:
1) hook up a Western Digital USB drive
2) make a full backup IMAGE using the Western Digital version of Acronis True Image
3) create a BOOT CD from Acronis TI
4) SWAP the hard drive for the SSD
5) BOOT to the Acronis TI DVD (with the USB hard drive attached)
6) RESTORE the previous backup image that's on the USB drive to the SSD
I also agree on the Samsung 830. Probably the 128GB version. It's currently considered the most reliable and there are many issues with many drives so it's a bit of hit-and-miss if you don't know what you're doing.
Save yourself the hassle and look for a Samsung 830 for $150 or less instead of a cheaper $90 that won't perform as well and may even lock-up completely.
Also, with an SSD, remember not to have the paging file on the SSD, make sure that the laptop supports AHCI on the SATA port(s) (this is a BIOS setting that is necessary for TRIM support with the SSD, a laptop might not have it by default, so you'll have to check), and you might also want to disable hibernation. Doing a drive cleaning (Windows has a decent tool for this), disabling unused services, uninstalling any programs that you don't use, and such are also good ideas. This should all be done prior to cloning the hard drive over to the SSD. You might also want a RAM upgrade to make up for the loss of the paging file. This would help ensure that the SSD has a long life-time.
If your laptop can't use AHCI on the SATA ports (it probably can, but maybe not), then you would be better off using an Intel 330 SSD. It uses a SandForce controller and this controller does not need TRIM nearly as badly as non-SandForce NAND flash controllers do to retain performance over time. Intel is really the only company who I'd trust with a SandForce SSD. IT would hurt battery life-time a little compared to the Samsung 830, but if you can't use AHCI, then you can't have TRIM and the Samsung 830 is much more susceptible to performance decreases from the lack of TRIM support, so it would be an almost necessary trade-off in this case. SSDs don't use a huge amount of power, so it wouldn't be a big battery drain at all, but it's considerable.
So, checking if your laptop supports AHCI is very important before you choose what SSD to buy. It probably does, but it wouldn't hurt to check and if it doesn't, then it could hurt to not check.