Adding RAM

Hello fellow members of Antionline.com. I have a Gateway 500GR

series tower. It came with 512mb of RAM. Last owner upgraded it

to 1gb of ram and it has another 256mb ram in it.

Anyways, I just checked out the specs and it maxes out at 2GB of

RAM. (machine is 10 years old) I purchased PNY DDR PC3200 1GB of RAM for it for like 30.00 bucks. This is

what the shop owner recommended. Well after I put in the screen (had lines through it)

looked fuzzy and after 5-10 minutes it would shut it's self off.

Which memory slot do I remove to install the new 1GB ram stick? Do I remove the 256mb ram stick and install the 1gb or ram here?

I tried both options and still get same results. Either option I try takes forever to load or it shuts it's self fown after 10 minutes.

Anyways, I returned everything back the way it was and now it seems the has a spinning cursor or after 5-10 minutes it shuts it's self down. This is my main machine I do strictly for email and invoices. I tried system restore but it failed to work. Please help. All help is greatly appreciated,