MemTest86 is a very good, and free for download, memory testing software.
It is available through a Google search.
You need the computer to run, in order to use it. So if you have two modules, remove one and test the other, then reverse the process to test the other module.
A correctly run test requires you run it for four hours or 7 passes, or more.
Luckily, your Dell Inspiron e1705 uses memory that is low cost. a 2 GB kit of matched pair will cost only $45.
Your laptop requires DDR2 PC2-4000, or DDR2 PC2-5300. All modules should be the same... you don't want one 4000 and one 5300 if you can avoid it... and a matched kit works best.
Avoid ValueRam if you are a gamer or do photo editing.
Good luck.