Hi and Welcome,
Drivers for USB connected HDDs are incorporated into Windows starting from WinME and W2k.
If Vista claims to not have drivers for this device, then there is either something wrong with the device or with your Windows installation.
Try other USB storage devices on your computer, and also try the HDD with another computer if possible.
Hm. Philips marketing names and the product numbers are often different. Made in China is also not uncommon for Philips branded products.
External 2,5" HDDs without additional PSU violate the USB specs since they draw much more power (~1000 mA on spinup) than allowed (500 mA max). It often works, but with some motherboards it just won't.