I think that is a 25Mhz quarz clock chip. Usually connected by two leads and possibly by it's casing to the old motherboards. since amount of contacts is at most 3, self soldering might be possible. (the text goes up)
However, if the motherboard is more recent (like 2006+) then the chip might be small enough that self soldering gets tricky.
Also possible downside is that whatever physical impact caused it to break off, MIGHT have caused other problems also so even if soldering would succeed, there is no guarantee that everything works.