Thank you guys for your responses.
If the extra $7 is worth it, I will definetly buy the Sempron 2600+, but then I would have only 128 mb of RAM because I am on a tight budget (this computer is for my friend who wants to spend only a minimal amount of money). So I have another question now: do you think it's smarter to buy the Sempron 2600+ with 128mb of RAM, or the 2.2Ghz Celeron -D with 256mb?
Thank you.