Lenovo ThinkCentre A57 (Series Type 9851)?

The question is what is your total part set and operating system. Normally, you do not replace the motherboard.
The computer case of all desktop pc brands is low quality, and power supply is cheap and low quality. DVDRWs are now inexpensive.
OEM versions of Windows 7 are tied to the motherboard, but it looks like your system was with Vista or XP.
It is not easy to keep OEM Windows 7, unless you bought the full retail version or know what you are doing.

The ram in that model shows DDR2, but motherboard accepts either DDR2 or DDR3 as two sticks if you ever changed. If you have DDR2, a new motherboard will be DDR3 so new ram.
You only upgrade a motherboard for a new CPU.

So, CPU, CPU cooler, Motherboard, RAM
What about the graphics card?
Power supply and case should be replaced anyway as lowest quality.
When I estimated one of these changes before, you replace everything but the DVDRW, and that is only $13.

Typically, you sell a computer instead of replacing a motherboard.

For the record, every branded PC I have seen is either a mini-ITX or Micro ATX, and that one should have micro ATX