First off. a 2.6GHz celeron isn't all that fast. The Celerons are the slowest of the Intel series and really aren't meant for heavy number crunching, apps, and gaming. It's not a powerful processor...probably about as powerful as an AMD XP2200+ or so really....
Also...256mb of what kind of ram..is it PC3200, PC2700, PC2100, PC133, PC100 what? We need to know that kind of info as well...but beyond that 256mb isn't very much these days. Most newer games require atleast 384 so a good amount to have now-a-days is 512mb and that's about standard whereas 256 was maybe a year ago or less...
Also...mercian is right...you should check to make sure your system isn't loaded with spywar and stuff. Use a program like Spybot Search & Destroy and ad-aware SE...use BOTH to thoroughly check your system, don't forget the updates... and
www.pc-cillin.com also offers a free online virus scan.
Basically it comes down to the fact that this is how Intel sells their computers. To people who only look at numbers. I'm not getting on to you, but if you want to ever learn about computers you need to look past numbers and get details. an AMD XP processor running at 2GHz would easily outperform that 2.6GHz intel especially because it is a Celeron...those ARE NOT IN ANYWAY performance chips...hate to disappoint you if you thought 2.6GHz automatically meant fast.
AMD's are better for gaming and can do more with slower clock cycles..that's why a 2GHz AMD XP chip can beat out a 2.6GHz intel besides the fact that the Intel is also celeron. Hope this has proved useful to you.
