I cannot unlock some pictures saved on my Olympus D-630 camera

Select the key icon from the Playback menu to protect/unprotect pictures. See page 33 of this manual: http://www.olympusamerica.com/files/oima_cckb/Stylus_1030_SW_Mju_1030_SW_Instruction_Manual_EN.pdf

You may download a copy of the manual here. The instructions for protecting/unprotecting pictures is on page 27.

If you already can connect your camera to your PC, then you should available do download pictures and videos. If you can find your video file from camera suite, open via Windows Explorer.
Camera usually will recognized as Removable Disk. There you can open the folders and browse all of saved files, including picture and video. Video files usually have film-like icon when set in thumbnail or large icon, or just see in detail setting so you can see the file's type.

Hope this help and if you feel this answer helpful, RATE please.

Never had a D-630, but the articles I read said yes, you can use a 2gb card.

You are so welcome. It is my pleasure!

To check pictures taken look for 'Review' button.
Your camera should show a camera logo/icon for
still pics and a video logo/icon for videos.
Check your manual.

As per the last persons solution the key icon does indicate you have locked the photo. First select the photo you want to delete, press menu, select playback menu, the key icon appears, press the weird shaped arrow button to the right of the OK; phot unlocks and allows to delete!!

Turn the wheel to the green arrow (playback mode) and turn the power on. Select Menu. The Playback Menu is automatically selected in the center, so click OK/Func. The first option is the key. Click OK/Func. You can then scroll through your pictures and turn the key on or off using the arrow keys. After turning it on/off on each picture, click OK/Func which takes you back to the main screen.

Whenever you are taking pictures of people within six feet of them, it is a good idea to turn on the flash - whether you are indoors or out. The Flash mode is easily accessed via the arrow pad on the back of the camera. Press the right arrow key, which has a lightning bolt icon, to enter the Flash Mode. Press the down key to select the lightning bolt icon and press “OK”. The flash will fire every time in this mode. Your outdoor pictures of people should improve in appearance since the flash will fill-in shadows normally apparent in outdoor shots.

The MACRO MODE is easily accessed via the arrow pad on the back of the camera. Press the left arrow key, which has a flower icon, to start the MACRO MODE. Press the down arrow key to select the flower icon in the menu. Then press the OK/MENU button; camera is now set for close-up photography. Remember to turn off the MACRO MODE when you begin shooting subjects beyond the focus range of the MACRO MODE.