Will a 366 pentium II processor from a thinkpad 390E work in a thinkpad 390 with a 266 pentium II processor?

the prcessory varies with clock speed and the speed for example a pentium 1 processor has a spped of 100mmx with aclock speed just 66mhz now the pentium 4 processor uses a spped of 3.0 ghz with a clock speed of 800mhz so there is deferance as the clock speed increase the speed of the computer increases

All your answers in once convenient page:
http://en.wikipedia.org/wiki/List_of_Intel_Pentium_microprocessors

yes, you can add memory to it, if the computer speed is not meeting up to your requirements.

your processor doesnt really have anything to do with the ability to get wireless internet. You can buy a wireless card and install it into your tower. You can buy one at any computer store or even walmart. This is assuming that you have a desktop pc and not a laptop. If you have a laptop you can buy a wireless card for it also. The easiest route would be to buy a usb wireless card, as long as you have a usb port available. Here is a link to a usb adapter:
http://www.newegg.com/Product/Product.aspx?Item=N82E16833130061&nm_mc=OTC-Froogle&cm_mmc=OTC-Froogle-_-Network+-+Wireless+Adapters-_-Zonet+Technologies++Inc.-_-33130061

Sometimes. Both the Pentium, Pentium II, many AMD, and some Cyrix processors used a socket 7. So depending on your motherboard and what two processors you are using it may work.

Well, there is not many places where you can buy a CPU for that motherboard. Also, you state that the current CPU is 250 MB but I think you mean the system memory is 256 MB. Looks like your CPU is 366 MHZ. You best bet is to look for a Pentium 4 motherboard/CPU and memory combo on ebay. You can probably find a P4 1.6 MHZ for barebones system for under $50.

Usually XP will work well on older systems, even ones that came with 98. The biggest thing will be if XP has drivers for the older devices such as the modem. Usually XP does a good job.

Check out this page with your exact model number
http://www-307.ibm.com/pc/support/site.wss/product.do?brandind=10&familyind=50191&operatingsystemind=49979&template=%2Fproductselection%2Flandingpages%2FonlinePublicationsLandingPage.vm&validate=true

No, this highest the P-II went to was either 400 or 450 Mhz. Upgrading a thinkpad CPU may be difficult. Considering prices on used laptops now, I wouldn't think it would be worthwhile, either.

Neil

Max CPU for IBM T20, 21, 22 is Pentium III FCPGA2 1000MHz (1GHz). Max memory is 512MB (2 x 256MB PC100/100MHz). Max hard disc is 250GB ATA. Newest BIOS is from April 2004 at the homepage Lenovo.

Since you have the slot for the wireless card, you can purchase an internal card for the machine, try Price Watch or Ebay. On the processor, the G40 came out with Pentium 4 2.0ghz, 2.4ghz, 2.6ghz, and 3.0ghz. any of these will work as long as they were designed for IBM Thinkpad. I buy most of the processors for my shop off Ebay. I would check there. If you do buy from Ebay, be sure that the processor came from an IBM machine.