'Service engine soon' light on 2001 Sentra... car experts?

[ryanghall]

If anyone here is really good with cars, I could use some help.

My girlfriend and I just bought a used car (2001 Nissan Sentra GXE) and the fifth time she's driven it, the 'Service Engine Soon' light has come on. The car only has 32,000 kms on it.

Is this something I need to worry about or has the computer likely just not been reset after the last oil change? Any car experts have insight into this?

Ryan