Short Trip to My Wit's End

This is only the second time I've posted for help, so I'm a little rusty. My problem: cannot defrag my disk. I have Windows XP with Service Pack 2, and I get the message "Disk Defragmenter Could Not Start" when trying to either analyze or defrag the disk. I also have AusLogics (per your recommendation from my malware removal problem over a year ago), and I get the message "No disks are available for defragmentation. This may be possible if current user does not have enough privileges to defragment any disks." This is my home computer and I am the administrator. The problem was noticed after a Norton Antivirus mystery deactivation. I worked with their tech support and got that working again (actually, they just gave me a free 2008 upgrade). I went back to them and they tried several things and stated it wasn't anything related to their system. I googled the problem and tried several suggestions, including making sure the virtual memory was set to "System Managed File" and the "No Paging File" was not selected. I tried doing the command prompt into system32 and registering dfrgsnap.dll and dfrgui.dll, and also installing dfrg.inf. I checked the services in my computer (and found my security alert turned off for some reason). Finally, I uninstalled Spybot, since one user mentioned that it could cause a defrag problem (I've had Spybot for several years with no problems, but I was desperate.). Too much information for an initial posting? Could use some help here. Thanks.