Do i have to enable 'memory remapping' in BIOS?
You should enable it.
Do i have to add '/PAE' in boot.ini?
Yes.
Do i have to add '/3GB' in boot.ini?
NO. Some programs can take advantage of this but the system could became unstable sometimes.
some reference worth to read:
http://bbs.et8.net/bbs/showthread.php?t=906641
http://www.chweng.idv.tw/swintro/ramdisk.php