RAM is not very expensive though - about 20 euros per stick (25 dollars?), depending on the speed and amount. You prolly do have more than one stick attached, meaning you can remove them one at a time to see which one is broken. That is as long as you know where they are located. If you don't, better not do it yourself. Not that it's very hard or complicated at all, but still...
If it is corrupt memory then the puter will have trouble doing other chores that used to be simple as well. It may have trouble booting, and you may need to try starting it several times before it can go to Windows. It may crash and restart with no apparent reason. Or just common software instability. Stuff like that. These thing may not be constant, but the occasional instability will occur.
If it's bad memory stick it'll have to be replaced at some point anyway, eventually it will fail completely.
