|That's more of a personal question. |
I have a computer that is 5 years old and I use it for school (not games) because it does just fine. I have upgraded the power supply, cooling fans, the hard drive and the video card over the years because the others failed or where too small.
The reason is I needed two computers, one for fun and one for work so it was cheaper to just keep fixing my old computer.
You may want to do the same. Its like asking when should I stop repairing my old car and get a new one. On the other hand if you need to use some of the new games, Windows 7, or Blue Ray then you will have to upgrade. The choice is yours.
P.S. as for your speed issue, it should not take 30 Minutes to boot up. It could either be doing a Virus scan or you have a Bot (Virus) on your computer or some incompatible drivers for old devices no longer connected to the computer.
You could use a registry scanner with an anti-virus to clean this up but you may consider a reformat and reinstall if you have every thing you need to do this.
Windows XP - System Disk with valid key.
MS-Office - Setup Disk with valid key.
Qucken - Setup Disk with valid key.
Driver - Need to download all of the drivers for your system and put them on a CD.
External Hard Drive - Or any media to back your files up to.
Time - Need about 2-3 Hours.
If you do not then may be you can take it into a shop to get some one to look at the registry for you or buy a reputable registry scanner.