In the list under the bold red Guides and Manuals subheading,
click on Hardware maintenance manuals.
Click on the blue -> [+] Click for files
Now click on the blue -> Hardware Maintenance Manual
(Above - 41d4550.pdf / 8.53MB )
This is a PDF file. May take up to 30 seconds, before the first page comes up.
At the top of the PDF file is the PDF file page number box. It is to the right of the Down Arrow.
If you know the page you want you can go to it page, by page, using the Down Arrow, or you can do this;
1) Put your mouse cursor in the PDF file page number box.
(Anything in page number box is now highlighted in Blue)
2) Type the page number.
3) Press the Enter key.
Also at the top is the Zoom In icon, ( + ), and the Zoom Out icon,
( - ).
Clicking on the Zoom In icon increases the view size.
Clicking on the Zoom Out icon decreases the view size.
Go to Page 263.
The Riser Card, or 'Daughter Card', is supposed to have
ONE -> PCI-Express x16 slot.
(Riser card is pointed out by the number 12 )http://support.lenovo.com/en_US/detail.page?LegacyDocID=MIGR-60400
Scroll the page down. Look under the bold subheading - Slots
"Slot 1: full length, x16 (16 Lane) PCI Express (graphics only)"
However it also states,
"Slot 2: half-length, x1 (1 Lane) PCI Express
Slot 3: half-length, PCI
Slot 4: half-length, PCI"
Hmmmm, okay, let's look at the 'Daughter Card',http://www.ebay.com/itm/IBM-Thinkcentre-S51-A52-PCI-PCI-e-x1-Riser-Card-/300562298930
Scroll the page down to the bottom to the photo.
The long white expansion slot on top is a PCI slot,http://en.wikipedia.org/wiki/File:PCI_Slots_Digon3.JPG
The black 'slot' underneath, is a combo of PCI-Express type expansion slots.
Looking at the contact pins;
A PCI-Express x1 expansion card, would fit in the slot all the way to the right, in the photo.
See the details printed in-between the white PCI slot, and the black slot underneath?
"PCIe x1 - ADD2 - R SLOT"
PCI Express x1 card - Add to the Right Slot
Means to me the entire slot, is used for a PCI-Express x16 graphics card.http://en.wikipedia.org/wiki/File:PCIExpress.jpg
The top Yellow slot is an example of a PCI-Express x4 slot.
Next slot down is an example of a PCI-Express x16 slot.
Next slot down is a PCI-Express x1 slot.
Next slot down is a PCI-Express x16 slot.
The last example is a PCI slot.
[Note* Color does not matter of the slots ]
From my perspective of looking at the photo for the Riser Card, I see the PCI-Express x16 slot, (Black), as being too wide in the middle.
Do not see that the gold plated contact pins of the PCI-Express graphics card, will make good contact with the contact pins, in that Black slot.
Haven't worked on a 'Pizza-Box' style of desktop computer in YEARS, so I am kinda' out of the loop.
IF, a PCI-Express graphics card does indeed make good contact, I suggest using a Low Profile one.
Just one example,http://www.tigerdirect.com/applications/SearchTools/item-details.asp?EdpNo=1380614&CatId=3669
Post back in a Comment, John.