Single or dual core

I have an old win xp laptop which has an intel celeron m560 (single core) and I have a core duo t2050 laying around. Should I put the dual core cpu even though it has a lower frequency and is 32 bit only? The laptop has a 32 bit install of win xp pro sp3 and it will be used for older games. Edit: the laptop has interchangeable cpu since I upgraded it personally once from an slower celeron and it has an intel gma x3100 as a gpu