Computer: Inspiron 8600; MSN Win. XP Home Edition V> 2002 Service pack 3: Porcessor 1.50GHz 2GB of Ram.System Drive Type  : NTFS
Physical Memory Available  : 1123488
Physical Memory Total  : 2096360
Virtual Memory Available  : 2056504
Virtual Memory Total  : 2097024

I have defrag my system and found a larger number of files that were still FRAGMENT. Can these files be deleted without hurting anything thus giving me more space on my hard drive? Some of he files are duplicates in everything except perhaps they MAY be one letter off in the name. What is the extention "ost" and  are they used . I have only 8.8 G Free space (23%).
These are some of the programs: Defender: CCleaner: Defraggler: Malwarebytes; McAfee:.ost files are MS Outlook files i believe...If CCleaner is not deleting them, delete NOTHING else.  23% free space is okay, however, if you intend on adding large amounts of programs or data, you'll have to purchase additional storage.kingsnite

If a defragger fails to defrag a file it is probably because the file is too large and/or free space is too small.  Another good reason is that the file is in use.  Deleting any such a file is certain to cause damage.

I think you have a fundamental misconception.

A defragger will report as fragments how many discontinuities occur in the disk storage of a file.
Each discontinuity has zero effect upon data quality - it only degrades speed of access.
Windows Explorer still allows you to delete the files, even though it is fragmented,
but it does not allow you to select and delete individual fragments.

NTFS file fragments are generally as above, and should not be deleted
FAT32 file fragments are generally as below. and may be deleted because data is already damaged.

Windows 98 etc would often break up a file into fragments and forget the order of use. I think on reboot it was SCANDISK that would find the debris and provide a new file name for each bit, such as File0001.CHK, File0002.CHK, File0003.CHK etc, but did not know where they came.  Deleting these *.chk fragments did no harm - the file was already destroyed and unusable.  Alternatively with a lot of patience one could inspect the CONTENTS and just possibly with luck perform copy and paste operations to rebuild a file.

Alan