I am a bit confused about determinig my processor.

When i run dxdiag, it lists my processor as Pentium III.

But when i check it on my system details (Start>Settings>Control Panel>System), i get it as Celeron.

Now which am i got to beleive?

Online Hardware Scan

Celeron processors with a speed rating of approximately 500MHz to 1.1GHz might also be referred to as a 'Pentium III' type of processor because this is the "full" Pentium version that they are comparable to.

In the same way, a Celeron rated at 266MHz to 433MHz might be referred to in some diagnostics tests as a Pentium II because that's the Intel "family" that it belongs to, along with the full-blown Pentium II processor.

You're right, though, that wouldn't be entirely correct so run the D-A-L.com Online Hardware Scan as Bear suggested and we'll be able to confirm what you've got