I currently own a Dell Inspiron 1520 that I bought in July 2007. When I bought it, I ordered it with 2GB of dual-channel, DDR2 PC2-5300 memory. Fast forward to today. I've discovered that 2GB doesn't seem to be enough at times for Vista Premium and Windows 7, so I decided that it was time add more memory. I went to Crucial.com and ordered two 2GB sticks of PC2-6400 memory, part #CT758807. The total price was $54.23 including tax. Yes, I should have asked before I bought it, but it isn't too late to cancel, either. Here are my questions: 1) Is Crucial still a reputable brand for memory? Will I experience any compatibility issues? I remember reading their ads in PC World magazine claiming "guaranteed compatibility," so I assumed that they are a safe choice. And of course, I used their system scanner tool to make my purchase. 2) Did I pay a reasonable price for the memory? I did a search on NewEgg and found the price to be comparable to Kingston. Is Crucial branded memory worth the added cost (if any) over the generic memory that you find at Fry's Electronics? 3) Will I notice a significant improvement in performance with 4GB of memory and PC2-6400 (as opposed to the current PC2-5300)? I understand that my O/S will only recognize between 3 to 3.5GB. However, will I actually benefit from this memory upgrade, or am I just wasting my money? I only use FireFox, iTunes, Word and AIM on a daily basis, yet my system uses well over 1GB of memory and I sometimes get the "low on memory" warning. I wonder if I actually need more memory, or if I have a "memory leak" somewhere. Thanks!