Whoa... near impossible I'm afraid. I mean, with KM75.1?? XP?? Javascript??
(With that amount of 256 I'd rather recommand KM1.6beta26 and win98 and of course block JS and all sorts of other stuff, plus occasionally a RAM defrag, then 50 tabs become realistic :cool
As basics: switch on the Privacy toolbar (if enough space), and allow JS only where really needed.
The normal settings are found in Edit>Configuration (shortcut F2), a few in menu Tools, and tons of additional hidden settings on the page about:config, as usual with Gecko browsers. Filter for keywords.