Your profile does not state where you live, but here in the UK we have a company called “Quiet PC” which can supply a totally silent PC if required. This is done using a huge passive CPU cooler, so that no fans are needed. Strictly speaking the computer will only be completely silent if solid state drives (SDD) are specified; but I have Solid State Hybrid Disk Drives (SHDD) in which a chunk of solid state memory passes information to and from a normal Hard Disk Drive (HDD). There is a very slight sound when the computer is first switched on, but after that it's completely silent however hard it's working. This very quiet or silent technology does cost a little more, but the extra is well worth while for musical applications such as Hauptwerk.
An alternative is to place the system unit in an adjacent room, and run leads through the wall to keyboard, mouse, monitor etc., and/or to use wireless devices where possible.
Quiet PC have a useful website whereon you can specify a PC to your own requirements, and judge the cost of various specifications. I will give their url as it may be helpful wherever you live; I would imagine that a similar service is available in other counties. I have no connection with the company other than as a satisfied customer.
http://www.quietpc.comI am a little concerned that your computer “exploded”, though I have heard of a motherboard catching fire. Perhaps those of us who leave our computers on most of the time need to extra aware of the possible fire risk.