CPU: Intel(R) Pentium(R) 4 CPU 3.00GHz
CPU speed: 2.99 GHZ
RAM: 3 GB
OS: Windows XP service pack 3
Video card: NVIDIA GeForce 8800 GTS 320mb OC
Hard drive: 150 GB, (have 45 GB free as of now and can uninstall some stuff if I have to)
MainBoard: Dell Precision 370 w/ 775 LGA socket.
Also I'm a Battlefield fan and i play Battlefield 1942, Vietnam and 2 local coop w/ 64 bots and it lags like crazy (primary reason for upgrading). I understand these are older games so i dont know if they work the dual core. Someone told me BF would then only use one core but then i wonder if that one core is powerful enough to run 64 bots with no lag.
You'll have to check with Dell to see if there are any BIOS updates that will allow you to use the E7400 in that motherboard. Chances are, you won't be able to though. Most likely that board is limited to P4s so you will more than likely need a new motherboard for the E7400.
as for reinstall - quite possible
it would be fun to just drop the cpu in and see what happens - or uninstall everything in device manager, shut down, swap cpu, restart = moment of truth.
windows might no go for it
do the bios upgrade first tho
and back up all files you value first
it worth trying - perhaps some research on google would discuss a cpu upgrade withoout reinstalling windoze
if dell has no bios upgrade, tell them they are morons
if the board goes useless, look into Phenom II 550 Black Edition, plus Gigabyte MA790XT-UD4P on newegg.
pouring more money, other than a simple cpu, into socket 775 is an investment in an end-of-life scenario.
spintel does stuff like this - even tho the socket is the same, and should upgrade easily, they make changes that might prevent the newer cpu from working in the existing older mobo - it's complicated - check with dell first.