Midi Piano is the simplest virtual keyboard and midi player around. Drag any midi file onto it, change speeds with the slider and you're ready to go. The simple record and playback features let you practice along with any scale or group of notes you wish to work on.

Anvil Studio is the best free MIDI software I have found yet. With it you can edit MIDI files or create your own from scratch. Here is where you can type in your tempo change for the MIDI file:

Click the word "on" to mute a track. Click again and the track will "solo" (play only that track). Click a third time and the track will return to "on":

If you only want to change the tempo of a MIDI file I suggest playing it in Windows Media and right click on the icon in the upper right corner to bring up the following menus:

Audacity is the best free recording software available. Just plug a microphone into your sound card (usually the pink input) and press the record button. If you want to add reverb, find their Gverb module shown below. The presets won't do much good for you so go here for better presets and a short tutorial.