What will I lose if I reset my samsung Galaxy SI (GTi9000)? I've had this phone for two years so all my photos are saved on the actual phone (not a micro SD card). I'm wondering if I reset it, will I lose all the photos saved on my phone? I'm not bothered about losing the apps just my photos I'm concerned about.
That very much depends on a) where exactly the photos are stored, and b) how the factory-reset is implemented on the device. As you can find out via the factory-reset tag's tag wiki (just hover your mouse over a tag and select the 'info' link to access its wiki), a factory reset will remove all your data and the apps you've installed. It usually does not touch the SDCard (external or internal).

Still: if you have the possibility (and your question does not seem to imply trouble booting your device into normal mode), why not copying everything you are concerned about (and which you can access) to another device, such as your computer, before doing the factory-reset? With that, you would be on the safe side.