Why isn't This Ram Working In My Computer?

hey guys i have a compaq presario 5000.  It takes pc100 memory and is supposed to have a max memory of 512.  I bought one 256 stick from archmemory which works great but I bought some 256mb pc100 sticks off of ebay and none of them will work in my computer.  I also bought a stick of pc133 which i have hear is backwards compatable with pc100 machines and that didn't work either.  Did I miss something or did i just get bad ram modules?
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check ram to see if its ECC, you cant mix and match...
downside is they sold u bad memory, i wouldnt trust ebay for memory anyway but thats my opinion....

good site to check for memory compatiblity is kingston.com or crucial.com
they have a search guide where you can select your computer brand/model number and it tells u what memory is compatible and if the info you supply them is correct, it tells you the capacity of memory and how it can be configured, such as single with any config or dual meaning if you want 512 that u will need two 256's, etc etc...

check those sites to verify the system specs for the ram
danielwebbAuthor Commented:
neither says ecc.
Older systems require low density memory.
As a general rule 16 chips on a 256 MB (PC100 or PC133) module is low density.
There are exceptions....
High density memory is cheaper so if you "got a deal"...........
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i know that many Compaq's are "picky" about memory brands, i only use kingston for them; and they always work.
Just a thought

You might try the memory individually in the system to determine if they work.  I've know different brands of memory to work well within their group but bring in an outsider (different brand) and all they do is fight.  System Blue screens and won't work.  

Above recommendations to check Kingston.com and Crucial.com are excellent.  Again as recommended Great place to obtain your memory.  If a problem exist have life time warranty and my experience is they fulfill that warranty without question.

Hope this Helps
nobus you are right on the button. Compaqs may be by far the pickiest I've seen when it comes to memory..especially older memory. My guess is that the ebay stock is either bad(no surprise there) or just not compatible. As for the PC133 stock...some PC100 systems can use them but that always seems to be a trial and error scenario. another thing to know is that you stay away from mixing memory(always a recipe for disaster). The best option is to buy from systems manufacturer or as said above...crucial or kingston. Brand names tend to be picky as opposed to clones...especially when it comes to things like PSUs and memory.
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