Yeah, though if you have a Pentium, expect it to run a little hotter than the Athlon.
Mine runs at 45 degrees C idle too by the way, and I have an AMD, so this seems about the normal.
Now, don't worry if this increases a little bit more than that, especially if its under load from programs, games, etc.
You should start worrying when it gets to about the 70 mark, so you should keep way below this, try to run below 60 degrees C at all times when running the PC, even at full load, okay?
You can set temperatures in Bios, which will start a warning sound when it gets to a certain temperture, and you can then set another one if it gets much hotter to turn off the PC (del at bootup, and it'll be in one of the menus, not sure which), so you can set this temperature for the alarm at about 60 degrees C, adn to turn the computer off if it reaches about 65 degrees C.
Though even 70 degrees C wouldn't fry the processor, but it could start slowing it down, adn it would be in danger of burning up.
If its a Pentium, do note that they are very good with overheating, and if the fan ever stopped working, the CPU's are very good at detecting this. What would then happen is, it'd slow down the core voltage and speed until the temperature reached a safe level, as to not damage the main core of the CPU, until you turned the PC off and replaced the fan.
I hope this helps