Your temps are fine, my 2400+ XP would run at 64C IDLE! when I had it in a case with no case fans, and the side panel open, now I have that processor in that same old case, but it has the coolermaster jet heatsink on it with some AS5, but I got a jerry rigged CPU Fan setup consisting of two fans stacked, spinning opposite directions, but both blow air the same way, creates more pressure between the fans when they spin opposite but blow the same, so it stays down at 54C, but yeah your temps aren't too bad, and after better heatsink and fan it'll probably go down 10C easily depending on what heatsink you get.
Also, in my bios the only thing I have found access too is the frequency (133). I cannot find the multiplier.
You might want to consider investing in a better OC'ers motherboard then, because I'm going to assume you also don't have access to the AGP:PCI Bus which needs to be locked when raising the Frequency past it's normal operating system which without having the Multiplier Option, upping the frequency is your only choice, and without an AGP:PCI Bus lock or the ability to change it, then even raising the FSB becomes and option that's not longer valid =/