displaymacbook pro
I have a MacBook Pro (15-inch, Early 2011). I want to hook two Dell monitors to it. They have VGA and DVI ports each.
I will be using the current DVI port on the MacBook Pro.
Will the Thunderbolt port work with a non-Thunderbolt monitor if I find a Thunderbolt to DVI-D adapter?
There are many types of DVI adapter, I could type a load of stuff or just point you at Wikipedia.
The key point is that there is no such thing as a DVI adapter. It's just a generic term that covers the overall outline of the cable end, but what you really have is either a DVI-I or DVI-D adapter, in either Single or Dual link capability. Or it may be a DVI-A. Or there are others...!
It's possible that your splitter cable must be of the dual link types, characterised by the longer horizontal bar pin, and your Thunderbolt adapter may or may not be. Shouldn't matter which type, either I (Integrated with analogue signal in the pins above/below the horizontal bar in addition to digital) or D (Digital only) as I imagine you are not subsequently adapting them down to DSUB further down the line, the only thing that matters is if they are both dual link.
So it looks like you need a Thunderbolt/MiniDisplayPort to DVI Dual link - the official apple one is the digital only one without the analogue pins (DVI-D Dual Link), and thus should work, if you are worrying that you do not have the same pinout (i.e. you have DVI-I Dual Link on your splitter, and it looks as though the analogue ones have nothing to connect to) then don't worry, it won't need them.
EDIT - Additional Info
After the comments, I have decided that you have a DMS-59 connector that looks like this:
So what you really need is a MiniDisplay > DMS-59 adapter, and my google-fu suggests that this is not looking like a possibility, I think you would be better served abandoning this cable, and looking for a total replacement, Mini Display Port > 2 x DVI (Single is fine, I or D if you have 2 ports). This may also be a pain to find, and you may end up needing a MDP/Thunderbolt to Dual Link DVI, followed by a Dual Link DVI > 2 X Single Link DVI splitter cable!
The mini DisplayPort to DVI adapter will work great, so your 27" monitor is in.
The VGA monitor is problematic. HDMI and DVI share almost identical digital video signals, so any HDMI to DVI adapter (like the included one) has few (if any) conversion chips in it and the output DVI port will be DVI-D (digital only). DVI to VGA adapters also don't have conversion chips because they use DVI-I or DVI-A ports (A is analog only and I id both analog and digital): they take the DVI analog signal and move it straight to the VGA port. Unfortunately, that means that you cannot go from HDMI to VGA via DVI. You'll need a more expensive converter like this or this.
tl;dr: You can't go from HDMI to VGA without a converter; see the links for examples. For the dual-link DVI you need, the adapter you mentioned that will use the Thunderbolt port will work excellently.
Best Answer
I have the same MBP. It only has a single displayport/thunderbolt output, which can drive a single monitor. The only way for it to drive multiple external displays is to use a daisy chained Thunderbolt display, or an adapter that drives multiple displays from a single input (Matrox makes one) or possibly a usb driven adapter.