To answer the OP.
The PP wins, PSOE comes in a close second. Based on March 10 polls, PP wins an absolute majority (barely) and Aznar retains power.
Aznar won't be relying upon regional/separatist parties to retain power, so there will be less accomodation of the catalan/basqe agendas. This will translate into a continued hard line on ETA (particularly after that groups aborted earlier attempt to sway the election) which will see more of that groups assets rolled up.
One might think that a lack of a de-facto Spanish surrender to Islamists would lead to continued efforts to score a high profile hit, but OTL doesn't actually show much evidence that the withdraw of troops from Iraq actually bought Spain any passes from the self-proclaimed jihadis. Nonetheless, no Madrid bombings means that the various incompetents and bumblers (such as those involved in the whole Leganes mess) who came to light in the investigation keep their positions - so something down the road is inevitable.
Outside of Spain, not much really changes
Aznar will not be attempting to buy his way back into Franco-German favor during the Consitutional negotiations - which will either result in stronger Spanish & Polish voting rights, or no agreed text at all. Doubt the final disposition of the text would differ, however.
The Spanish detachment in Iraq remains for another year or so beyond OTL. The anti-Iraq War movement loses one source of inertia/confirmation but retains others.
Efforts to reduce Dept of Agriculture controls on imports of some spanish foods (salted ham / pata negra in particular) continue to receive a mild push from the executive which they lost in OTL.
Chavez & Castro lose some 2004-2005 political cover, but the absence won't change their policies materially.