Will 2gig of RAM on Vista really improve my PT, PAHud, poker speeds?

[88keyz]

Currently using a P4 2.8ghz, 1gig Corsair RAM, and ATi x1600 512MB video card on Vista Business.

Occassionaly my computer lags up and I miss hands (when it unfreezes, the hands go by in fast forward).

I'm wondering if its a RAM issue or what?
If so, will another gig of RAM show some results?

Please help. I'd like to know whether to spend $100 on RAM or to just save that money to buy a new computer down the line.

Thanks