I thought this would be failing hard drive, didn't think memory would cause a stutter (vs. blue screens, etc,). To check drive get the SMART data from the drive. Goto device manager, find brand of hard drive (there are only a few makers) goto their web site, download diagnostic. Display smart data. Run short and long drive tests. GThen force a chkdsk by open computer, rite click on drive, tools, error check when asked say on next boot.
Smart data's job is to monitor and predict drive failure. Not perfect, but I've replace working drives called out by smart data.
From wikipedia.. http://en.wikipedia.org/wiki/S.M.A.R.T.
S.M.A.R.T. (Self-Monitoring, Analysis and Reporting Technology; often written as SMART) is a monitoring system for computer hard disk drives to detect and report on various indicators of reliability, in the hope of anticipating failures.
edit: look for fields like "Seek Error Rate" and "Read Error Rate" and "Reallocated Sectors Count" and "Recalibration Retries or Calibration Retry Count" and "Soft Read Error Rate" .... in the smart data. The tool should format the raw data for you and add labels like these copied from wikipedia.