That is pretty hot and could be the cause for reboots , is it a pentium or an amd?
Try to clean the fan and heatsink , or maybe replace it to get the temp down.
But that wouldn't explain the errors you have , looking at youre
hjt and ewido log there aren't to much problems there and those should be gone now , btw you didn't post a new
hjt log yet. (please attach it to a post)
I would run a test on youre memory with memtest:
http://www.memtest86.com/
And run a diskcheck ,in "my computer" , rightclick on youre hd(s) and select tools/error checking/check now.
Also give this a go:
go to start / run and in the run window type in:
sfc /scannow >enter
Have you XP CD in youre drive, and it'll run itself, replacing any missign or damaged protected XP files.
EDIT: did you also run the app that Zimbo posted?
Would you be able to download Burnintest from the following link:
http://www.passmark.com/download/index.htm
Then run the program in safemode and run scans on your hard drive as well as your memory.
Let us know whether it finds any problems.