Can i upgrade my PC to core2Duo/Quad-core ?

I have a Lenovo Desktop PC. I want to upgrade its Pentium 4 Processor to a Core 2 Duo or a Quad-core. Will there be any improvement in gaming and other software performance by this upgrade? If yes, then suggest me a budget CPU with decent performance in gaming (complimenting my Geforce 8400 GS) and other tasks and could survive for 2 to 3 years decently. I can’t upgrade anything apart from the CPU (b’coz of just 300W PSU Oem fitted which has a special power slot for my Lenovo LCD Monitor therefore can’t upgrade the PSU).
Also I have few other queries:
Does the Core 2 Duo or Quad-core consume more power than a P4 cpu ?
Also I get the details about the Motherboard name and Model as “To be set by O.E.M” in the CPU-Z and EVEREST Ultimate software. So how can I know if my motherboard is upgradeable to a Core 2 Duo and so I can’t even get the BIOS update, (I’m just getting a Chipset Driver update from the Lenovo Support webpage). I just have the following System Details of my PC :
Chipset : Intel 945G
Motherboard : “To be set by O.E.M” (in CPU-Z) but in Everest it shows “Intel i945G”
Socket : LGA 775
Processor : Intel Pentium 4 3.06 Ghz HT with EM64T
GPU : XFX Geforce 8400 GS 256 MB
RAM : 2 GB DDR2 Dual-Channel

Yes, a product from the Core 2 series, in all likelihood, will consume more power than your Pentium 4... but the difference will be negligible since the 8400 isn't exactly a heavy-power consumer.

I wouldn't risk it unless you can find out for sure. It's usually not a BIOS issue, its a hardware/circuitry issue. Did you get your motherboard/computer BEFORE the C2Ds came out?

http://www.pcmech.com/forum/showthread.php?t=172820

It'd be nice to be able to upgrade to a C2D, but I wouldn't risk it unless you're willing to RMA products.

Also, a motherboard for Lenovo is pretty much a guarantee that you won't be able to overclock, which is an easy way get another 15-40% out of your CPU, depending on which of the Core 2 series you get.

I don't think 945 series support..C2D...