Agree with Diodorus Siculus the second processor is by far the best but it will also be more expensive, to be honest for what you say you use it for I don't think you'd notice the difference. I'm not up on the Intel chips as I prefer AMD but if these 2 chips take different sockets they will need different motherboards, regardless of which they will also need different memory. Celerons are "cut down" Pentiums the same as Semprons are "cut down" Athlons. They are budget chips cheaper and slower.
There you are you see but there are other differences that may be of more importance, the 1100 cannot take a graphics card its onboard graphics only, the 5150 which is what I think you mean as I couldn't find a 5130, comes with a basic PCI Express graphics card which you could upgrade later plus has twice the memory and look at the warranty as well, its different. I was asked by a friend to recommend a cheap PC for his mother, they were looking at the 1100 and the 3100. I ended up recommending to her the 1100 with the 15" TFT and upgrading the warranty to one year on site. Total cost £304. I also suggested she may want to upgrade the memory later on, checked out Crucial and they were just under £20, the same from Dell was I think about £70. Now I know this woman and I know what she uses her existing computer for, word processing, perhaps a spreadsheet, surfing the internet etc and this PC will be fine for her. But in general I would not recommend to people to get a PC that the graphics cannot be upgraded on as many of them will later on see a game they wish to play and discover that they can't.
FREE Upgrade to 19" TFT AMD Athlon™ 64 3200+ Processor Genuine Windows® XP Home ASUS A8N_VM PCI- X Mainboard 512MB DDR400 Memory 160GB Serial ATA Hard Drive 128MB GeForce 6100 Graphics 19" DVI Flat Panel TFT Display Sony 16x Dual Layer DVD Writer 5.1 Channel Surround Sound Audio Logitech Desktop KB & Optical Mouse Classic Warranty-3Years parts & lab.