Where to get phoenix rom bios plus update?

Unless you are trying to a just fix a problem with a hardware incompatibility and even for which the motherboard has the maker or even Dell have released a fix specifically relating to the issue,that you should not flash the BIOS.It is only a certainly not a "recreational activity", it is normally done due to only when a new Windows version or such things as RAID arrays need to be then accommodated, or may be similar events.If a BIOS flash goes bad (and sadly a reasonable % do) then often the motherboard can be economically unrepairable, which in a Dell system means the new specific Dell motherboard which has exact the same model or the installed Windows version will not work, requiring a new copy.A failed BIOS flash leads has to be a high expense in other words, until you are sure and have absolute evidence it is needed, don't go there!