Hi Sky Express,
If all that is broken is Acrobat, try a reinstall, as acrobat 6.0 is out it may be worthwhile anyway.
If the browser seems to have lost associations with several types of file then it may be worth reinstalling the browser first. You don't say what browser / version. If it is not up to date then you will improve your security by doing an update. If you are using windows then a visit to
http://windowsupdate.microsoft.com should sort out Internet Explorer (And outlook express etc. - there were 20 new bugs this month!) If you already do the regular updates excuse me teaching you to suck eggs!
If you are not on broadband it might be worth checking out some computer mag cover disks to see if there is one with the latest software you need on it. the acrobat and Internet explorer downloads are quite large.
If you are on WIndows XP and this trouble started after any system changes you may be able to "roll back" to before the changes. Have a look in Windows help - i have, fortunately, never needed it so can't offer guidance here.
Hope you get it fixed.
Memetic.