I think I'm the opposite of most people - as DM I don't have a computer, and as a player I do.
Okay, even as DM I user a word processor for campaign notes, but I find that having physical papers I can spread out and write on works for me. Plus the act of updating the files later with things that happen in game helps reinforce them so a year later I havent forgotten.
As a player, I use a computer to speed myself during combat. For example, fro a 7th level druid I have an excel sheet that auto-calcs my wildshapes (and I have written up stat blocks for all summonable monsters already modified by my feats). For an epic level high magic campaign with a 22nd level character and a huge amount of buffing (from multiple PCs), debuffing, dispelling, and polymnorphing, I have a spreadsheet character sheet that's not designed to print out, but rather to handle everything and just give me the number. It's organically grown around the character, one of these days I hope to make it more general. But it can handle that I've got 14 different buff spells up, am arcane striking, power attacking, have higher ground, polymorphed into a frost giant, and am shaken.
Of course, making it became a hobby in itself, and I think I spent more time making that sheet then playing the character sicne that game meets infrequently.
Cheers,
=Blue