How many RAM can i add and who are the manufacturer? I have two RAM chips in my Mac. How can i get to know, how many of them can i upgrade? I mean, it could happen, that one (or even two) of them are soldered on…?

And, how is it possible to get out who is the manufacturer of RAM? - three are only cryptical codes, like 0xAD00000000000000… I wouldn't like to buy RAM from manufacturer, who doesn't match with the RAM already installed.

It goes about the following hardware:

MacBook Pro
15 Zoll, 2,4 2,2 GHz
Prozessor  2,2 GHz Intel Core 2 Duo
NVIDIA GeForce 8600M GT 128 MB
Serial Number: W874214LX91

RAM:

BANK 0/DIMM0:
Size:   2 GB
Typ:    DDR2 SDRAM
Tact Frequency: 667 MHz
Status: OK
Manufacturer:   0xAD00000000000000
Part Number:    0x48594D503132355336344350382D59352020
Serial Number:  0x00006170

BANK 1/DIMM1:
Size:   1 GB
Typ:    DDR2 SDRAM
Tact Frequency: 667 MHz
Status: OK
Manufacturer:   0x7F7F7F7F7F7FC100
Part Number:    0x4232594A55533733464E3120202020202020
Serial Number:  0x00000058
Apple did not solder RAM in those days, so you should be good to go. As far as the manufacturer is concerned, it really doesn't matter. As long as the modules are from a good (and ideally the same) manufacturer (crucial has been good in my experience), match the required specs which you can find at sites such as http://www.appleserialnumberinfo.com by entering your serial number, you'll be good to go.

I would also advise that you use the same sizes of memory modules in both banks. You currently have an imbalance, which can negatively impact performance.