upgrading ram

I have two ram slots in my pc with one 256mb ddr sdram. I can either buy 2x512 ddr or a 1x1gig ddr and wait to buy another 1gig stick later. my mobo and graphics card are both old and at minimum specs for winxp. I can see at least a four month wait until I could buy the second 1gig stick.
Will the 256ddr i have already work ok with the new 1gig until i could replace it with another gig?

Since you said it's old, it's not likely to use dual channel memory, get the 1 gig first and keep the 256 installed.
Then when funds permit get the 2nd 1 gig.
There's no sure way to find out if both of them will play nice with each other...... I guess you can try to make sure their timings are the same, find cpu-Z and compare the timing of your old 256mb ram with the new 1 gig.

thanks for the assistance. Ill do the things you suggested.

make sure the memory you get is the same brand if you run them together
as well as the same speed
also be sure you put them in the correct slots if it is dual channel

>>4
this is good advice. Not very eloquent or technical, but still good advice. You will not fuck up if you follow advice like this.

This is not what you normally hear out of Anonymous

FORCE THE DIMMS IN BACKWARDS THAT MAKES THE SPEED GO 2xGHZ

not sure if the i can do dual channel. I havent seen anything in the documentation for my pc parts that even mentions that. Are heat risers a necessity?