Vista - Performance Low-Cached Memory High

Sometime within the past couple weeks, my computer has been running slower than normal, even when i have no programs running. Simple tasks such as opening an explorer window or program now much longer than normal. The performance tab in my task manager shows total memory 4GB, cached memory at over 3GB and free memory at only 30KB and sometimes 0KB. I've looked in the processes tab and have noticed nothing out of the the ordinary, and i've run a full scan of Kaspersky and Malwarebytes and found nothing.The problem usually happens a couple minutes after i boot up and login into windows. Prior to the sluggishness my free memory stayed between 1 and 2 GB. Now its between 75 and 0KB I have no idea what could be the problem, as i've had no major hardware or software additions/changes in the past couple weeks. Any help would be appriciated!!!
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System Info:
Model: Gateway FX-7811 Laptop
Processor: Intel® Core 2 Duo CPU P8400 @2.27GHz DDR3
Memory: 4.GB RAM DDR3
System type: 64-bit Vista Home Premium (Service Pack 2)
Graphics Card: NVIDIA GeForce 9800M DDR3 w/ 512 dedicated video memory
Monitor: High Resolution 17” WUXGA 1920x1200 widescreen