I have a laptop of compaq brand whose modle no is presario C700 in which intel celeron microprocessor is installed. 512 MB ram is installed i want to update it 4 improving its speed. i want to setup a more powerful processor. which type of processors i can install in it ,up to what sizes of ram it will support.

I found the manual on the net that gives you instructions on replacing components if you're not sure how, it can be found here.

RAM upgrade
The Compaq Presario C700 uses DDR2 Laptop RAM as shown below.
The motherboard of the Presario C700 has two RAM slots, one of them will be occupied by the 512MB RAM (running at 667MHz) module you have at present. This leaves one more that can accomodate a DDR2 667Mhz card of up to 1GB or you could get two 1GB DDR2 800MHz (the faster DDR2) cards and remove the 512 leaving you with a wopping 4GB of memory, that'll definately speed it up. Just remember the Presario C700 can only have up to 2GB of RAM so don't go higher than that or Windows will not boot for some reason.

Processor upgrade
The Presario C700 supports any Socket P, Core 2 Duo or Pentiun Dual Core chips. The fastest processor you can get is the Intel T8300 2.4GHz Core 2 Duo Processor with 3MB L2 cache and an 800MHz FSB

For a full list of compatible processors go to page 9 of the user manual found here.