Upgrading RAM

That is a great idea because now you can upgrade to a gig later if you want
it may be cheaper to use 2 chips though

It may be ok... depends on the laptop - some max out at 512 (usually the older ones) and some can handle 1GB. (Some can handle more).  You didn't post which laptop you have so we can't see for certian.  But as Titanium Sniper points out - this leaves the other slot open so you can actually have 768 MB of RAM using one 256 and one 512.

It's a good idea for upgrading purposes;  but if your laptop is dual-channel capable you'll only run in single-channel mode (slower memory bandwidth) until you add a second identical chip.

I doubt if the laptop came with 2 128 chips that it had dual channel

... note that most current Dell laptops are dual-channel capable;  but older ones generally aren't.   If you post your model number we can tell you both your max capacity (as leew noted) and whether or not it's dual channel capable.

What model of laptop is it?  Checking the details at Dell for the max RAM capacity will answer this question.

"... I doubt if the laptop came with 2 128 chips that it had dual channel..." ==>  I tend to agree; but Dell does ship notebooks with relatively small memory configurations.   For example, see Page 97 of this manual (http://support.dell.com/support/edocs/systems/ins1300/en/om/om_en.pdf), which shows that the Inspiron 1300/B120/B130 models have dual-channel memory buses;  but these models were, and still are, sold with only 256MB.

OK, to clarify things...

1.) the laptop is a Dell Inspiron 1100 Series

2.) It DEFINITELY had two 128M chips for a total of 256M.

3.) They are DIMMS chips -- dual in-line bla bla...

4.) I NOW have ONE 512M chip in ONE slot and the other slot is empty. Total RAm now is 512M, of course.

I ONLY WANT TO UPGRADE TO 512M.

I was asking if its OK to have ONE 512M chip or should I have bought TWO 256M chips and used both slots.

Oh yes, and the MAX RAM is 1024M. But I dont want that for now, just 512M.

The computer will work fine and much faster than before

Go to http://www.memoryx.com and find your machine. It will tell you what memory you can successfully use on your machine.

I'd guess that the 1100 does not support dual channel memory (the Dell documentation for your system doesn't say one way or the other) -- in any event your PC will work fine with the 512mb chip (and you may as well leave one of the 128mb chips installed as well).

Your system does, however, use an Intel 845G chipset, which DOES support dual channel access (doesn't mean Dell's using it that way).

If you really want to know if it COULD operate in dual channel mode, do this:

(1)  Download, install, and run Everest Home Edition from http://www.majorgeeks.com/download4181.html

(2)  Look under Motherboard - Chipset  and see what the Memory Controller section shows.   It should show a "Type" and an "Active Mode".   Your Active Mode will be single channel;   the question is does your type show "Dual Channel" ??   If it does, you would get better performance with 2 256MB modules.

... NOTE:  If it DOES show a "Dual Channel" type and you want to confirm that the system actually supports it;  just put both of the 128mb modules back in, and run Everest again -- if the Active Mode is now Dual Channel then you'll know the system supports it.

I was asking if its OK to have ONE 512M chip or should I have bought TWO 256M chips and used both slots.<<

go with what you already bought.  if it doesn't work just bring it back to the place where you bought it and tell them it doesn't work in your system and you want two 256MB modules

cf101

Just to be sure it's clear ...  the answer to your question ("... Is that OK? ...") is absolutely YES.

The only residual question is whether or not your system would run in dual channel mode if you had two sticks -- which, if so, would give you better memory bandwidth.   The notes in my last post show you how to determine that.