Upgrading to 7.4 will not delete the logs, as the logs reside in the iDrac and the tool just draws the logs from there. I do suggest if you are going to go to 7.4 that you remove the 5.2.0 version completely before proceeding with the install. 
Hi, I am working on PE 2950; Windows server 2003 - Dell Open Manage Server Administrator v5.2.0The server has been rebooting randomly several times with the log message : " System board OS Watchdog: watchdog sensor for System Board, power cycle was asserted "Do you have any suggestions regarding this problem ?Thank you !
PowerEdge 2950 Random Reboot