My x90 has a problem squeling belst all the time ..i put two new ones on it and same trouble ...what have i got to do to stop this ?  besides spraying it evertime i use it with belt dressing .

Belts squeal for one reason - they are slipping - you need to find out why and correct it.

They could be worn or loose - and if you allow them to slip for a while they can glaze, so no amount of tightening prevents them from slipping.

Another much more rare cause is the pulleys being out of alignment, forcing the belt to run at an angle so that it slips - make sure the bolts holding the alternator in place are all present.

Thanks...thats helps me in the right direction !!

Get the next smallest length size of belt, and tighten the crap out of it,
that's what I had to do, use a big pry bar to get it tight enough

Wild

there was a rubber shortage a while back and they were adding more plastic to the belts, I went threw the same thing a couple of years ago, if the place you got them from had some of those belts laying around you probably got one or two of them.

Get the next smallest length size of belt, and tighten the crap out of it,
that's what I had to do, use a big pry bar to get it tight enough

Wild

That is a good way to take out water pump and alternator bearings, or break the alternator brackets/bolts/ears (heard of it happening before).
I wouldn't recommend tightening it tighter than what the spec is.

drenalin...Is a seal or something leaking, allowing oil to get on the belts or pulleys?  Oil, antifreeze, AC oil will all cause the belt to slip, if it gets on it or the pulleys.  Maybe try spraying the pulleys down thoroughly with brake cleaner before you put the belt on the next time, in case there is some oil or something on them.
I've never had much luck with using belt dressing.  It allows dirt and stuff to stick to the belt too and that makes it want to slip.

Well don't tighten the "crap" out of it, but until it stops squealing,
For the record I have never had pump or alternator bearing problems
but I did get rid of that damn noise 

Wild
 

The belt dressings can work, but only for very minor issues. Too much and it creates it's own slippage issue.

Do you have the original alternator installed, or an upgrade?