I'm in the beta and have gotten a few games in and I notice my computer keeps lagging and I suspect that its because I may not have enough RAM to support it. I'm curious if anyone has gotten the specs for playing a smooth game my rig is pretty old but here are my specs  

Windows XP, Pentium 4 3.00ghz, ATI Radeon 3650 HD 512MB, 1.25GB of Ram. 
 
Yea I know my specs aren't the best and I'm still running an AGP graphics card but I can seemingly play alot of games smoothly without much issue. I'm just curious as why the game has hiccups when all the settings are on low on my desktop but when I play on my PC which has seemingly less specs it runs pretty smooth. The suggested settings SC2 puts me at is medium/high and I can play it in that mode on my desktop pretty fluently its just the hiccups during games or when scrolling the minimap becomes unbearable. I want to say its because of my processor/ram combo but I'm not the savviest guy for CPU's. Any suggestions would be good preferably ones that would cost me the least.

You'll be fine on low.  The specs are posted all over the beta forums so check it from there.
 
My 7900 GT can run it pimp in my parent's PC.

From the wiki:
 PC Minimum Requirements:     

• Windows XP SP3/Vista SP1/Windows 7
• 2.2 Ghz Pentium IV or equivalent AMD Athlon processor
• 1 GB system RAM/1.5 GB for Vista and Windows 7
• 128 MB NVidia GeForce 6600 GT/ATI Radeon 9800 PRO video card
• 1024x768 minimum display resolution
• 4 GB free hard space (Beta)
• Broadband connection