Hi Ahmad,
You can put it in, but there is no guarantee it will work. The laptop might be picky and want matched pairs, in which case you can just add another of the sticks you bought. But if it isn't picky, then it will just run in single channel mode, which means the RAM will be a little slower, but it will see the 768 MB. Since you already have the 512 MB stick, just pop it in in place of one of the 256 MB sticks and see if it boots. The worst thing that could happen would be that it just wouldn't boot, and you will need to get another 512 MB stick.
Having 768 MB will increase performance, but in that laptop, the biggest thing you can do to increase performance is get a 7200 RPH hard disk, since the 4200 RPM hard disk is very slow and is the bottleneck in most cases.
You can put it in, but there is no guarantee it will work. The laptop might be picky and want matched pairs, in which case you can just add another of the sticks you bought. But if it isn't picky, then it will just run in single channel mode, which means the RAM will be a little slower, but it will see the 768 MB. Since you already have the 512 MB stick, just pop it in in place of one of the 256 MB sticks and see if it boots. The worst thing that could happen would be that it just wouldn't boot, and you will need to get another 512 MB stick.
Having 768 MB will increase performance, but in that laptop, the biggest thing you can do to increase performance is get a 7200 RPH hard disk, since the 4200 RPM hard disk is very slow and is the bottleneck in most cases.
