I purchased a new Acer Aspire One D250 netbook a few days ago and am interested adding RAM. My old notebook, an HP Pavilion dv6810us, appears to use the same 200 pin SODIMMs that the netbook uses. My question is whether or not it is a good idea to put used RAM in a new machine.

http://en.wikipedia.org/wiki/DDR2_SDRAM
In principle, yes.

But the older modules might have a lower clock rate, which would lead to inferior performance.

Also, how many RAM slots does the netbook have? It seems to me that such a small form-factor would have only one slot. You can't add more memory without taking the stuff you already have out.
Plus there are limits on what you can mix-and-match even if there are two slots, and one of them is free for you to use.

http://en.wikipedia.org/wiki/DDR2_SDRAM
In principle, yes.

But the older modules might have a lower clock rate, which would lead to inferior performance.

Also, how many RAM slots does the netbook have? It seems to me that such a small form-factor would have only one slot. You can't add more memory without taking the stuff you already have out.
Plus there are limits on what you can mix-and-match even if there are two slots, and one of them is free for you to use.

The older modules have a higher clock rate (667mhz), which is the max for the new machine. The older machine has 2 SODIMMs, one 1GB and one 2 GB. The new one only has one slot, but the SODIMM currently in it is 1GB. The manual states that I can use a 2 GB SODIMM.

The manual states that I can use a 2 GB SODIMM.

put it in because it will need it ,what windows version in on the netbook