Trying to add a PCI-E card to your Lenovo Thinkcenter computer? The Thinkcenter S51 part numbers 8098, 8171, 8172, and 8173 will beep with code 4 2 3 3 if you try to install any PCI-E card, besides a PCI-e x1 card. The system only supports PCI-e x1.
Please read the official hardware maintenance manual from Lenovo, for your Lenovo Thinkcentre S51. The bezel is removable but must be replaced with a PCI-e x1 card only. If you feel your Thinkcentre computer is having this problem then make sure to check with Lenovo support to see if this affects your particular model.
You can find PCI-e x1 cards from many popular online retailers like the ones listed in a google search. You might also want to contact a local retail computer store to see if they have any if you don't want to purchase one online. Just ask them if they have any PCI-e x1 cards.