Quote from PaulRon:
thx max - maybe i got the terminology wrong but i'm just looking to paper trade old data to get used to the feel of trading and strategies
Various firms offer simulators, which allow you to papertrade. TOS is one. Ninja Tader is another. Look them up in the software section.
Backtesting platforms allow you to program trading strategies or systems and see the results. They vary a lot in complexity and the level of programming knowledge necessary. Fidelity's Wealthlab , TradeStation and Amibroker are three off the top of my head. I'd suggest going through the software section here or googling backtesting software.
I think one of the biggest benefits of backtesting is you can see the effect of stop loss levels. You can also convince yourself that indicator-based strategies will not work. Certainly it is possible to curve-fit a system and convince yourself it is the key to riches, then blow up when you try to trade it. the other side though is if a system won't work on historical data, why would you ever use it with real money?