Back in 2007 i built for a friend of mine a Athlon 64x2 system running Vista.
IT's an Asus motherboard socket 939 with 2GB DDR max 4GB and a Athlon 64 x2 4200. She used it for 8 years then got a win 8.1 laptop in 2015 which she just cracked the screen and made unusable.
She's not ready to buy a new computer so we are reviving the Athlon 64x2
The Old hard drive has bad sectors so it's gone and new cmos battery was installed. Also purchased 2GB of additional memory.
So I have a old Never used 250GB IDE drive and a old 500GB SATA that I only used for 1 month. both tested and passed. System wil boot from both IDE and SATA.
Since the system is old and we dont'want to sink money into it I was planning to yous the 250GB IDE and install windows 7 32bit which I have a licences for.
I can also get a licenses for windows 8.1 64bit and install it on the 500GB SATA.
Which would you folks recommend? i know win 7 will work well because my folks have a win7 AMD Turion laptop and works well.
If Win 8.1 64 bit can work well on this old system then she has a computer for 2 to 3 years.

Second question , the Motherboard has 4 memory slots and a max memory of 4GB. It had 2GB already and i just purchased an additional 2GB of the same memory same manufacture and everything.
When I put them all in the bios only reads 2.5GB. Why? i tested them all individually and they seem to work.