I just throwed away Diskeeper (2007) to the bin
OK it runs in background without trouble
BUT, i just found it split up the System Windows files (specially hiberfil.sys & pagefile.sys + some others) which i defragment with Sysinternals PageDefrag on boot
WWW Link, and above all, i also founded that even running in background 24/24 i got a statistic off "average fragments number per file = 1,02" (which is a lottttttttttttt)
Note: a manual defrag on same disk (which is a very new one) which is about 40 Go used on a 150 Go partition, takes nearlly 24 h

Though i just installed Auslogics Disk Defrag version 1.4.15.306, and it defraged 100 % of files in about 30 mn ...

it's freeware, and brings me back 6% of free RAM