Baseline for Computer Setup & Maintenance
What do you need?

Hardware and Basic Software

Laptop vs. tower/desktop?
Usable display and controls?
Protective covers?
Operating system?
Power supply/conditioner?

Third-party software probably needed

Antivirus/antispyware 
Firewall
Registry maintenance tool
Defragmentation tool
Backup plan

Regular maintenance and backup

Clear temporary files
Backup
Defragment
Apply Microsoft updates (automatic updates every Tuesday, but you need to be Internet connected to get them. Options are available if you can't connect)
Check for new versions of device drivers and apply.