Default [Q] SD Card keeps appearing to be damaged

Hello all!

I have a 4GB Micro SD card, that came with my mother's old phone and worked fine. I found it and put it in my phone, but after a few days it appears to android as "DAMAGED" all of a sudden. My phone is HTC Desire Z. It happened after I formatted it to delete a load of pictures my brother had taken after he went on my phone (hes young lol!) When I use something like USB Mass Storage, it will happen then, after reboots it happens, all different times. I have checked it in Windows, I have done slow formats on it, (I have yet to try formatting it under my linux system, hoping this will do the trick) I have done everything. Please help me as I dont want to have to buy a new one just yet!

Thanks, Will.