Question #1: Do I need to update my VIA chipset? There is one generic (I use generic because it is for ALL VIA chipsets), it is called VIA Hyperion 4 in 1 driver. It contains IDE, SATA, RAID, Audio, USB, IrDA and intergrated graphics.
It is a good driver system. I like the VIA chipset. It is not the fastest, but I have found it to be the most stable.
Question #2: Do I need a bigger power supply? You really should get a 300W power supply. However, it is not required. The question is the amount of power your sysem requires. Most P4 systems will need a 300W to be stable.
Power supplied to:
CPU & Fan
Floppy, CD-ROM, CD-RW, CD-DVD & Harddrives
Case & power supply fans
And then there is your ATI card. These use a lot of power in order to help keep the temperature cooler.
All of these starting at one time is too much, which results in no boot up or very unstable system. Trading power for heat. That is bad.
However, if you are using a one harddrive, only a CPU fan, one CD-ROM, floppy and ATI video card it should be able to work properlly with just a 250W power supply.