I used 3Dmark01 and the scores were comparable with and without the stick of 512 RAM, but my computer seems faster with the stick in, so I'll keep it in for now.
Is there any software that will tell me the best type of RAM that my mobo can handle (i.e. PC3200, etc)? If not, maybe there is something that can tell me the type of mobo I have and then I can check it out to see up to what type of RAM my mobo supports?
Dell XPS 420
Core 2 Quad Processor Q9300 (2.50GHz 1333FSB) with 6MB cache
4GB DDR2 SDRAM at 667MHz
256MB Radeon ATI HD 2600 XT
Western Digital 7200 rpm 500GB SATA HDD w/ 16MB DataBurst Cache
Sound Blaster X-Fi Xtreme Gamer
Dell 2408wfp LCD
6X Blu-ray and 16X DVD+/-RW
Altec-Lansing THX certified 5.1 ADA995 Dolby Digital Speakers
Vista Home Premium