Hi, my g1 has problem to read the sd card, when i try to use the camera, the phone says it does´nt have, and windows XP do recognize the phone

Need a little clarity on what your saying XP does recognize the SD card when you mount the phone to the computer, or it doesn't?

Well here is what you can try. and just remember ALWAYS ALWAYS ALWAYS do this before removing your SD card from your phone.

Settings>SD card & phone storage>Unmount SD card

Now if your phone has "Unmount SD card" blacked out then don't worry about just go ahead and remove the SD card.

Take the card and put it in a card reader and put it in your computer. Go to: Start>My computer> (and the drive corresponding to the SD card.) and then try to open it. If a window comes up saying something like drive E: is not formatted, Format now? and then Ok or cancel well if this comes up it could be one of three reasons; the SD card is not properly formatted, SD card is damaged, or the SD card reader is not working properly. So before trying to format the SD card try another card reader or try it on a different computer. If that doesn't work try to format the SD card. If formatting the SD card doesn't work, you may need to buy another one. If you do decide to get another one check Amazon.com they have good prices for the SD cards however if you prefer local buying best place to go (that I've found) is Radio Shack. They always have sales on the MicroSD cards. One other thing. For some reason. SanDisk Micro Sd cards seem to work the best for the G1. The transend cards are utter **** and worthless. Avoid buying them anytime your in the market for a new SD card or USB flash drive.

If you need further help feel free to check out xda-developers.com